4. The sum of 4x3 +6x²+2x-3 and 3x³ +3x²-5x-5
is
A. 7x² + 3x²-3x
C. 7x³ +9x²-3x-8
B. 7x³ +3x²+7x+2
D. 7x +9²-3x² - 8