the atomic number of phosphorus is

Answers

Answer 1

Answer:

The atomic number of phosphorus is 15.

Explanation:

It’s found after Si(Silicon) and before S(sulphur)


Related Questions

A spacecraft orbits the Earth at height of 1600km. Calculate the escape velocity for the spacecraft.
[G= 6.67×10^-11Nm^2kg^-2, mass of the Earth= 5.97×10^24kg, radius of the Earth= 6.37×10^6m]​

Answers

Answer:

what do u need help with

Explanation:

Calculate the escape velocity for the spacecraft. [G= 6.67×10^-11Nm^2kg^-2, mass of the Earth= 5.97×10^24kg, radius of the Earth= ...

Diffraction spreading for a flashlight is insignificant compared with other limitations in its optics, such as spherical aberrations in its mirror. To show this, calculate the minimum angular spreading in rad of a flashlight beam that is originally 5.90 cm in diameter with an average wavelength of 610 nm.

Answers

Answer:

The answer is "[tex]1.2566 \times 10^{-5}\,rad[/tex]".

Explanation:

As per the Rayleigh Criterion the minimum angular spreading, for a circular aperture:

[tex]\theta_{\mathrm{min}}\approx \sin\theta=1.22\,\frac{\lambda}{d}[/tex]  

[tex]\theta_{\mathrm{min}}=\mathrm{1.22\,\frac{\left( 610\,nm \right)}{\left( 5.90\,cm \right)}=1.22\,\frac{\left( 610\times10^{-9}\,m \right)}{\left( 5.90\times10^{-2}\,m \right)}}[/tex]

                               [tex]=1.22\times 103.389 \times 10^{-7}\\\\=1.22\times 1.03 \times 10^{-5}\\\\=\mathrm{1.2566 \times 10^{-5}\,rad}[/tex]

A solenoid passing by a current of 5.0 A generates a magnetic field at its diameter of 50 μT. Thus the number of spirals per length scale is:

A. 5.0 / π Spear / m

B. 10 / π Spear / m

C. 20 / π Spear / m

D. 25 / π Spear / m

Answers

Answer:

D. 25 / π Spiral / m

Explanation:

Given;

current, I = 5 A

magnetic field strength, B = 50 μT = 50 x 10⁻⁶ T

The magnetic field strength is given as;

[tex]B = \mu_0 nI\\\\where;\\\\\mu_0 \ is \ permeability \ of \ free \ space = 4\pi \times 10^{-7} T/A.m\\\\n \ is \ the \ number \ of \ spirals \ per \ length\\\\n = \frac{B}{\mu_0 I} = \frac{50 \times 10^{-6}}{5\times 4\pi \times 10^{-7}} = \frac{25}{\pi } \ spirals /m \\\\[/tex]

Therefore, the correct option is D. 25 / π Spiral / m

Two Carnot air conditioners, A and B, are removing heat from different rooms. The outside temperature is the same for both rooms, 314 K. The room serviced by unit A is kept at a temperature of 292 K, while the room serviced by unit B is kept at 298 K. The heat removed from either room is 4430 J. For both units, find (a), (b) the magnitude of the work required and (c), (d) the magnitude of the heat deposited outside for A and B conditioners respectively

Answers

Answer:

(a)  333.77 J

(b) 237.85 J

(c) 4763.77 J

(d) 4667.85 J

Explanation:

Temperature of source, TH = 314 K

Temperature of A, Tc = 292 K

Temperature of B, Tc' = 298 K

heat taken out, Qc = 4430 J

Let the heat deposited outside is QH and QH' by A and B respectively.

[tex]\frac{Q_H}{Q_c}=\frac{T_H}{T_c}\\\\Q_H = \frac{4430\times314}{292}=4763.77 J[/tex]

Now

[tex]\frac{Q_H'}{Q_c}=\frac{T_H}{T_c'}\\\\Q_H' = \frac{4430\times314}{298}=4667.85 J[/tex]

(a) Work done for A

W = QH - QC = 4763.77 - 4430 = 333.77 J

(b) Work done for B

W' = QH' - Qc = 4667.85 - 4430 = 237.85 J

(c) QH = 4763.77 J

(d) QH' = 4667.85 J

What is Plancks Constant? Need it ASAP

Answers

Answer:

The Planck constant, or Planck's constant, is a fundamental physical constant denoted h, and is of fundamental importance in quantum mechanics. A photon's energy is equal to its frequency multiplied by the Planck constant. Due to mass–energy equivalence, the Planck constant also relates mass to frequency.

Theory:

Planck postulated that the energy of light is proportional to the frequency, and the constant that relates them is known as Planck's constant (h). His work led to Albert Einstein determining that light exists in discrete quanta of energy, or photons.

E = hf

[tex] \sf \: h = 6.626 \times {10}^{ - 34} \: kg \: {m}^{2} {s}^{ - 1} [/tex]

A spring has a spring constant of 5 N/m and is stretched 10 m. What its U,?
a. 50 J
b. 70 J
c. 90 J
d. 250 J

Answers

Answer

I am not sure but it is may be 50J

I hope that's, this answer is fine.

describe the forest ecosystem with examples​

Answers

A forest ecosystem describes the community of plants, animals, microbes and all other organisms in interaction with the chemical and physical features of their environment: Specifically, a terrestrial environment dominated by trees growing in a closed canopy — a forest, in other words.

Hope this helps you buddy! :)

magnetised hacksaw blade is cut into two pieces..can there be two poles on both sides??​

Answers

Answer:

yes

Explanation:

because the dipoles are not arrange the same way they were in the full hacksaw

An empty cardboard box falls from a high platform. Through the use of special equipment it was found that the energy of the cardboard box at the top of the fall was more than the energy of the box at the bottom of the fall. Explain.

Answers

Answer:

The mechanical energy of the cardboard box, M.E. = K.E. + P.E.

Where;

P.E. = The potential energy of the cardboard box = m·g·h

K.E. = The kinetic energy of the cardboard box = (1/2)·m·v²

Where;

m = Mass of the cardboard box

g = The (constant) acceleration due to gravity ≈ 9.81 m/s²

h = The height of the cardboard box

v = The velocity of the cardboard box

At the top of the fall, where h = The height of the platform = [tex]h_{platform}[/tex], and v = 0 (the box is initially at rest at the top), the M.E. is given as follows;

[tex]M.E._{top}[/tex] = P.E. + K.E. = m·g·[tex]h_{platform}[/tex] + (1/2) × m × 0² = m·g·[tex]h_{platform}[/tex]

However, at the bottom of the fall, the height of the box, h = 0, the velocity of the box, v = 0, therefore, the total energy at the bottom, after the box comes to rest, [tex]M.E._{bottom}[/tex] = 0

Therefore;

The total energy of the box at the top of the fall, .[tex]M.E._{top}[/tex] = m·g·[tex]h_{platform}[/tex] was more than the total energy of the box at the bottom of the fall,

[tex]M.E._{bottom}[/tex] = 0

Explanation:

Write a balanced nuclear reaction for one complete cycle

Answers

Answer:

H + H ------> He + energy. He + He -----> H + H + He.

Explanation:

Hydrogen having one proton and no neutron fuse with hydrogen having one proton and one neutron forming helium atom with the release of photon. After that two helium atoms combine together forming two hydrogen atoms having one proton each whereas one helium atom having two protons and two neutrons present in their nucleus so the end product of this reaction is hydrogen atoms and helium.

in a cathode-ray tube, particles are fired at the screen. What are these particles

Answers

Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons.

why football players boots have spikes their sole
Give short and sweet answer​

Answers

Answer:

it helps with balance and speed.

"The football shoes have spikes or studs because the studs or spikes provides larger frictional force than normal shoes while running on the grass. The studs prevents player from slipping on the grass and help to run faster and change direction quickly without slipping"

Answer:

they provide a larger frictional force than normal shoes while running on the grass.

e. write unit of the following physical quantities

Answers

Answer:

electric current=ampere(A)

force=Newton (N)

area=metres square(m^2)

power=watt(w)

density=kg/m3 

amount of substance =mole per cubic meter (mol/m3).

volume=cubic meter (m3),

Answer:

thanks for brainlist brother.........

The image shows a landform created by Earth’s forces.

A dip in a mountain range between two plates.

Which describes this landform?

anticline
shearing
syncline
tension

Answers

The term that best describes the landform "dip in a mountain range" is C. Syncline.

Syncline is a term to refer to a fold of the Earth's crust caused by the tectonic effects of the earth's dynamics. A synclinal fold is characterized by being a concave fold, that is, in the shape of a U.

According to the above, answers A, B and D are not correct options because they refer to different shapes of the Earth. Therefore, the landform shown is syncline.

Learn more at: https://brainly.com/question/17137827

Answer: C

Explanation: E2022

Squids rely on jet propulsion to move around in water. A 1.5 kg squid at rest suddenly expels 0.12 kg of water backward to quickly get itself moving forward at 2.8 m/s. If other forces (such as the drag force on the squid) are ignored, what is the speed with which the squid expels water

Answers

Answer:

The speed of water is 32.2 m/s .

Explanation:

Mass of squid, M = 1.5 kg

mass of water, m = 0.12 kg

velocity of squid, V = - 2.8 m/s

Let the speed of water is v.

Use the conservation of momentum,

Momentum before expelling the water  momentum after expelling water

M x 0 = (M - m) x V + m x v

0 = - (1.5 - 0.12) x 2.8 + 0.12 v

3.864 = 0.12 v

v = 32.2 m/s

una caja en reposo se traslada 93 cm con un peso de 67N en un tiempo de 9,89h.¿cual es la aceleración la masa y la fuerza de dicho objeto

Answers

Answer:

a. Acceleration, a = 1.47 * 10^{-9} m/s²

b. Mass = 4.57 * 10^{10} kilograms

c. Force = 67.12 Newton

Explanation:

Given the following data;

Distance = 93 cm to meters = 93/100 = 0.93 meters

Weight = 67 N

Time = 9.89 hours to seconds = 35604 seconds

Initial velocity = 0 m/s (since it's starting from rest)

Acceleration due to gravity, g = 9.8 m/s

a. To find the acceleration, we would use the second equation of motion;

[tex] S = ut + \frac{1}{2} at^{2} [/tex]

Where;

S is the distance covered or displacement of an object.

u is the initial velocity.

a is the acceleration.

t is the time.

Substituting the values into the equation, we have;

[tex] 0.93 = 0*35604 + \frac{1}{2} * a*35604^{2} [/tex]

[tex] 0.93 = 0 + \frac{1}{2} * 1267644816a [/tex]

[tex] 0.93 = 633822408a [/tex]

[tex] Acceleration, a = \frac{0.93}{633822408} [/tex]

Acceleration, a = 1.47 * 10^{-9} m/s²

b. To find the mass

Weight = mass * acceleration due to gravity

67 = mass * 1.47 * 10^{-9}

[tex] Acceleration, a = \frac{67}{1.47 * 10^{-9}} [/tex]

Mass = 4.57 * 10^{10} kilograms

c. To find the force;

Force = mass * acceleration

Force = 4.57 * 10^{10} * 1.47 * 10^{-9}

Force = 67.12 Newton

(Q008) Magnetic anomalies are a. found only on the seafloor. b. measured with an instrument called an inclinometer. c. defined as the angle between which a compass needle points and the longitude at that point. d. places where the magnetic field strength is either greater or less than the expected strength.

Answers

Answer: D. places where the magnetic field strength is either greater or less than the expected strength.

Explanation:

Magnetic anomaly refers to the change in the magnitude of the magnetic field of the Eatth with respect to the location's expected value.

Magnetic anomalies are places where the magnetic field strength is either greater or less than the expected strength. Therefore, the correct option is D.

An aluminium block of mass 1 kg is heated by an electric heater for 3 minutes and a temperature rise of 15 °C is recorded. If the electric heater is connected to a voltmeter which gives a reading of 30 V and an ammeter which gives a reading of 2.5 A, calculate the specific heat capacity of the aluminium.​

Answers

Answer:

the specific heat capa city of the aluminium is 900 joules per kilogram per °C.

Am I right please?

The mass of earth 6*10^24kg its radius is 6.4*10^3km now calculate due to gravity on earth

Answers

Answer:

Explanation:

in your textbook, they have a formula like this:

g=mass of earth*G/R^2

G=6.67*10^-11

apply to this

we have g=6*10^2*4*6.67*10^-11/(6.4*10^3*1000)^2=9.78

Explain why a person travelling in a bus falls forward when bus stops suddenly

Answers

Answer:

Cause of Inertia of Motion

Explanation:

It can be explained as follows...when the moving bus suddenly stops, the lower part of the body of the passenger contact with the bus suddenly comes to rest while the upper part of the body tends to retain its state of motion due to inertia. As a result, the passenger is thrown forward.

Water falls down as a stream from a tap. Why does it not scatter?​

Answers

Answer:

as it hits the ground it's dispersed and this causes it to move in different directions

1. Una carga Q1 = + 12 μC se coloca a una distancia r = 0.024 m desde una carga Q2 = + 16 μC. a) Determina la magnitud de la fuerza electrostática que actúa sobre las dos cargas, Q1 y Q2. b) ¿Es la fuerza la atracción o repulsión? 2. Determina la intensidad del campo eléctrico a una distancia radial de r = 48 mm desde una carga de Q = 24 μC. 3. Una carga Q1 = 24 mC se coloca a una distancia r = 0.032 m desde una carga Q2 = - 12 μC. a. Determina la cantidad de energía potencial eléctrica que tiene la carga Q1. b. Determina el potencial eléctrico en la posición de Q2.

Answers

Answer:

1. a. 3,000 N

b. Repulsión

2. 46.875 × 10⁶ N/C

3. a. 81,000 J

b. 6.75 × 10⁹ V

Explanation:

1. Los parámetros dados son;

Q₁ = +12 μC, Q₂ = +16 μC

La distancia entre las cargas, r = 0.024

La magnitud de la fuerza electrostática, F, entre cargas se da como sigue;

[tex]F = k \times \dfrac{Q_1 \cdot Q_2}{r^2}[/tex]

Donde, k = constante de Coulomb = 9.0 × 10⁹ N · m² / C²

Por lo tanto, obtenemos;

F = 9.0 × 10⁹ × 12 × 10⁻⁶ × 16 × 10⁻⁶ / 0.024² = 3.000

La magnitud de la fuerza electrostática, entre las cargas, F = 3000 N

(b) Dado que tanto Q₁ como Q₂ son cargas positivas, y las cargas iguales se repelen entre sí, la fuerza es la repulsión.

2) La intensidad de un campo eléctrico, E, se da como sigue;

[tex]E = \dfrac{k \cdot Q}{r^2}[/tex]

La magnitud de la carga, Q = 24 μC

La distancia donde se mide el campo, r = 48 mm = 0.048 m

Por lo tanto, E = 9.0 × 10⁹ × 12 × 10⁻⁶ / 0.048² = 46,875,000 N / C

La intensidad de un campo eléctrico, E = 46,875,000 N / C = 46.875 × 10⁶ N / C

3. La magnitud de las cargas son;

Q₁ = 24 mC

Q₂ = -12 μC

La distancia entre las cargas, r = 0.032 m

un. El potencial eléctrico de una carga, [tex]U_E[/tex] , se da de la siguiente manera;

[tex]U_E = k \times \dfrac{Q_1 \cdot Q_2}{r}[/tex]

Por lo tanto;

[tex]U_E[/tex] = 9.0×10⁹ × 24 × 10⁻³ × (-12) × 10⁻⁶ /0.032 = -81,000

La energía potencial eléctrica entre la carga, Q₁ y Q₂= -81,000 J

b. El potencial eléctrico de Q₁ en Q₂, V₁ = [tex]k \times \dfrac{Q_1 }{r}[/tex]

Por lo tanto, V₁ = 9.0×10⁹ × 24 × 10⁻³/0.032 = 6.75 × 10⁹

El potencial eléctrico de Q₁ en Q₂, V₁ = 6.75 × 10⁹ V

help me guys, i am illiterate
if the mass of the moon 7.2*10^22 kg and and the radius is 1.7*10^6m , what will be the acceleration due to gravity of the moon ? what will be the weight of a person of 60 kg mass on the surface of moon ?

Answers

Answer:

A. 1.66 N/Kg or m/s²

B. 99.6 N

Explanation:

A. Determination of the acceleration due to gravity of the moon.

Mass of the moon (Mₘ) = 7.2×10²² Kg

Radius of the moon (rₘ) = 1.7×10⁶ m

Gravitational constant (G) = 6.67×10¯¹¹ Nm²/Kg²

Acceleration due to gravity of the moon (gₘ)

gₘ = GMₘ / rₘ²

gₘ = (6.67×10¯¹¹ × 7.2×10²²) / (1.7×10⁶)²

gₘ = 1.66 N/Kg

Acceleration due to gravity on the moon is 1.66 N/Kg or m/s²

B. Determination of the weight of a 60 kg person on the moon.

Acceleration due to gravity of the moon (gₘ) = 1.66 N/Kg

Mass of person (m) = 60 Kg

Weight on the moon (Wₘ) =?

Wₘ = m × gₘ

Wₘ = 60 × 1.66

Wₘ = 99.6 N

Thus, the weight of a 60 kg person on the moon is 99.6 N

the hydrometer with the density of liquid to be 800 kg metre per square is the volume of the submerged part of the hydrometer is 5 into 10 to the power minus 5 calculate the mass of the hydrometer​

Answers

Answer:

Mass = 0.04 Kg

Explanation:

Given the following data;

Density = 800 kg/m³

Volume = 5 * 10^{-5} m³

To find the mass of the object;

Density can be defined as mass all over the volume of an object.

Simply stated, density is mass per unit volume of an object.

Mathematically, density is given by the formula;

[tex] Density = \frac {mass}{volume} [/tex]

Making mass the subject of formula, we have;

[tex] Mass = density * volume [/tex]

Substituting the values into the formula, we have;

[tex] Mass = 800 * 5 * 10^{-5} [/tex]

Mass = 0.04 Kg

Why do ionic compounds make good conductors when dissolved in water?

Answers

Answer: The correct answer is B- The ions are free to move in water and carry an electric charge.

An airplane flying at 116 m/s. E, is accelerated uniformly at the rate of 9.2 m/s2, E, for 13 s. What is its final velocity in m/s?

Answers

Answer:

235.6m/s

Explanation:

you have to use one of the kinematic formulas the best that suits the question given in this case you can use v=u+at.since the time, acceleration and initial velocity have been given in the question

v=116+(9.2)13^2

v=116+119.6

=235.6m/s

I hope this helps

The needle in the following diagram rotates around a fixed point in the middle. Based on the information given, what way will the needle rotate when the current is applied?

Answers

Answer:

nods 40th anniversary rid off e 49en9 snns

(1) A string of constant thickness and length I cm is stretched by a force of T Newton. A
tuning fork stamped 256 Hz sets the string vibrating at its fundamental frequency.
Find the frequency of the string when:
(i) Its length is doubled and the tension constant;
(ii) the tension is doubled and the length constant.
2) State the effect of increase in the tension on a wire on its frequency.

Answers

Answer:

Explanation:

i) frequency is the square root of the quotient of Tension over linear density/ all divided by two times the length.

linear density and tension are constant, so the numerator remains constant

The length is doubled, so the frequency is halved.

f = 128 Hz

ii) Doubling the tension increases the frequency by √2

f = 256√2 = 362 Hz

2) If other factors remain constant, increasing tension increases frequency.

the power station uses some of its waste thermal energy to hear water for houses in a nearby town. State one problem of using waster energy in this way if the power station is far from town. Suggest a way of reducing this problem​

Answers

Answer:

Explanation:

By the time the hot water gets to the place where it can be used for heating, it will have lost a great deal of energy to the surroundings.

The way to prevent that from happening is to insulate the pipeline with fiber glass like house insulation. Of course since this is a physics question and not an engineering problem, you could move the power station closer to the houses to be heated.

The use of Insulating Layers with low Conduction Coefficients and radii greater than Critical Radius diminish Losses and gives important Savings in terms of Energy Efficiency.

The main problem of Transportation of Waste Energy through Long Distances is the heat transfer between the Fluid flowing through the Tube and Surroundings. Heat Losses are directly proportional to the Distance travelled by the Fluid.

A possible way to minimize this Problem is to isolate outer surface of Tubes with materials with low Conduction Coefficients. at Critical Radius, in which Heat Losses reach its theoretical Maximum, from which Heat Transfer tends to diminish at greater radii.

According to the Theory of Heat Transfer, the Critical Radius of the Insulating Layer is equal to:

[tex]r_{c} = \frac{k}{h}[/tex] (1)

Where:

[tex]k[/tex] - Conduction coefficient, in watts per meter-Kelvin.[tex]h[/tex] - Convection coefficient, in watts per square meter-Kelvin.

Using materials with low Conduction Coefficient minimize Thickness requirements and, therefore, overall costs tends to sink when [tex]r > r_{c}[/tex].

Hence, the use of Insulating Layers with low Conduction Coefficients and Radii greater than Critical Radius diminish Losses and gives important Savings in terms of Energy Efficiency.

An ant moves towards the plane mirror with speed of 2 m/s & the mirror is moved towards the ant with the same speed. What is the relative velocity between the ant and its image?​

Answers

Speed of ant-V_a=2m/sSpeed of mirror =v_b=2m/s

We know

[tex]\boxed{\sf Relative\:velocity(V_{AB})=V_A-V_B}[/tex]

[tex]\\ \sf\longmapsto V_{AB}=2-2[/tex]

[tex]\\ \sf\longmapsto V_{AB}=0m/s[/tex]

The vector difference between the velocities of two bodies : the velocity of a body with respect to another regarded as being at rest  compare relative motion

[tex]Relative velocity $\left(\mathrm{V}_{\mathrm{AB}}\right)=\mathrm{V}_{\mathrm{A}}-\mathrm{V}_{\mathrm{B}}$$$\begin{aligned}&\longmapsto \mathrm{V}_{\mathrm{AB}}=2-2 \\&\longmapsto \mathrm{V}_{\mathrm{AB}}=0 \mathrm{~m} / \mathrm{s}\end{aligned}$$[/tex]

What is relative velocity and its unit?

The relative velocity of an object with respect to another is the velocity with which one object moves with respect to another object. The unit of velocity can be referred to as the ratio of unit of distance and that of time. The SI unit of Relative velocity is meter per second.

What is absolute velocity?

The concept of absolute velocity is mainly used in turbomachinery design and defines the velocity of a fluid particle in relation to the surrounding, stationary environment. Together with the relative velocity (w) and the circumferential speed (u), it forms the velocity triangle.

To learn more about relative velocity, refer

https://brainly.com/question/24430414

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How does Higgins respond when Liza tries to stand up to him?He bullies her.He sulks.He is proud of her.O He withdraws his offer. An organism and its taxonomic key are shown below.An image of an organism is shown. The organism has two body regions with four legs on each side. 3 mm is written next to the image of the organism. There are no claw-like pinchers.Taxonomic KeyStep Characteristic Organism1 8 legs Go to step 2.More than 8 legs Go to step 3.2 One body region Go to step 4.Two body regions Go to step 5.3 One pair of legs on each body segment CentipedeTwo pairs of legs on each body segment Millipede4 Less than 1 millimeter long MiteMore than 1 millimeter long Tick5 Claw-like pinchers Go to step 6.No claw-like pinchers Spider6 Long tail with a stinger ScorpionNo tail or stinger PseudoscorpionWhich organism is shown in the image? Millipede Spider Scorpion Tick most naturally occurring oxygen is (-4)-(+2)= PLS HELPPP MEEEEEEE 11. Which of the following symptoms indicate acute rejection of a transplanted kidney? A. Edema, nausea B. Fever, anorexia C. Weight gain, pain at graft site D. Increased WBC count, pain with voiding To mail an envelope first class the us pot charges 0.32 cents for the first ounce and 0.24 cents for each additional ounce. Use an inequality to find the maximum number of whole ounces that can be mailed for $7.98 If you were a business owner how would you go about the sun exactly what product me to your business needs would you do all my sis drive to the store talk to the manager etc. asino Inc. expects to pay a dividend of $3 per share at the end of year 1 (Div1) and these dividends are expected to grow at a constant rate of 6 percent per year forever. If the required rate of return on the stock is 18 percent, what is the current value of the stock today? Please I need help :( Please help As soon as possible.. which of these transactions types increase how much you owe the credit card company A 69.0-kg astronaut is floating in space, luckily he has his trusty 28.0-kg physics book. He throws his physics book and accelerates at 0.0130 m/s2 in the opposite direction. What is the magnitude of the acceleration of the physics book? Help?! Please! Thank you!!!!!!! Help please guys thanks Choose a word below that has a different stress pattern from the others.politicsSeptembercompulsorydependent My Mother's cooking is______ than our neighbor's. ( A.better. B. good C. best. D. more good ) What is a pronoun and a noun Can humanity get rid of humanity What is the area of the triangle in heron's formula? Vit Nam c nhng tim nng g v ti nguyn du lch cho pht trin du lch quc gia (national tourism)trong iu kin hin nay (2021)?