Collect Like Terms $-7 \mathrm{x}^{9}+3 \mathrm{x}^{9}+18$ A) $-36 x+18$ B) $-4 x^{9}+18$ C) Can't Be Simplified
D)

Collect like terms.
- $-7 \mathrm{x}^{9}+3 \mathrm{x}^{9}+18$

A) $-36 x+18$
B) $-4 x^{9}+18$
C) Can't be simplified
D) $-4 x^{18}+18$