An even and an odd integer are multiplied together. Which of the following numbers could not be the square of their product?  Choices:
A) 36 B) 81 C) 100 D) 324 E) 900
81 = 9^2 so it can not be the square of an even number multiplied by an odd number.   The answer is 81.
<result>B</result>
An even and an odd integer are multiplied together. Which of the following numbers could not be the square of their product?