Simplify.
(3x^3 + 2x^2 + 10) + (3x^3 + 2x^2 + 10x)

A) 3x^3 + 2x^2 + 10x + 10
B) 6x^3 + 4x^2 + 20x
C) 6x^3 + 4x^2 + 10x + 10
D) 9x^3 + 4x^2 + 100x