Write a linear factorization of the function.

f(x) = x4 + 4x2

A f(x) = x2(2x + i)2
B f(x) = x2(x + 2i)2
C f(x) = x2 (x + 2i)(x - 2i)
D f(x) = x2 ( 2x + i)( 2x - i)