Can someone check this? Thanks! :)

Question

Which pair(s) of functions are inverses? There may be more than one correct answer.

a.) f(x) = x - 12, g(x) = x + 12
b.) f(x) = 3x, g(x) = 1/3x
c.) f(x) = 4x, g(x) = -4x
d.) f(x) = 2x + 1, g(x) = 2x - 1

My answer: A & C