B. If the end result from the second column is not 9, then the sum of the numbers in the first column is not equal to the sum of the numbers in the second column.
This is because the process described (adding the digits of the numbers and then adding the digits of the result until a single digit is obtained) is essentially finding the digital root of the sum of the numbers in each column. If the digital roots of the two columns are different, then the sum of the numbers in the first column cannot be equal to the sum of the numbers in the second column.