The question is:

Which of the following polynomials is NOT a perfect square trinomial?

A) x2 + 2x + 1

B) 4x2 - 4x + 1

C) x2 + 3x + 9

D) 16x2 + 8x + 1

E) all of them are perfect square trinomials

the way it is explained in my lesson is very confusing. I am very confused. please help me!