Kylie explained that (–4x + 9)2 will result in a difference of squares because (–4x + 9)2 = (–4x)2 + (9)2 = 16x2 + 81. Which statement best describes Kylie’s explanation?

A=Kylie is correct.
B=Kylie correctly understood that it is a difference of squares, but she did not determine the product correctly.
C=Kylie did not understand that this is a perfect square trinomial, and she did not determine the product correctly.
D=Kylie determined the product correctly, but she did not understand that this is a perfect square trinomial.