Hello from MrBillDoesMath!
Answer: C
Discussion:
h(x) = (f g)(x) = f(g(x)) and if
g(x) = x + 2 and f(x) = 3x^2 (choice C)
the h(x) = f(g(x)) = f (x+2) = 3 (x+2) ^2 as requested.
Regards, MrB
