Which of the following equations is equal to -x^2-4?

a. (-x-2i) (x+2i)
b. (-x+2i) (x-2i)
-2i) (x-2i)
d. (x+2i) (x-2i)

Definitely not D, because one of the x's needs to be negative, and the other should be positive so the x will end up negative when it is multiplied. 
I want to say the answer is C. (-x-2i) (x-2i)
Hope this helps :)

The correct answer is b