Answer: D. (x-6)(x-6)
Step-by-step explanation:
We have the following trinomial, which is also known as perfect square trinomial, because the first and the third term are squares:
(1)
First term:
Third term:
If we factorize this expression we have:
As we can see, the trinomial (1) has two factors:
and
Therefore, the correct option is D.