Simplify the Expression $-12 y+(-9 y)$ A) $-21 y^{2}$ B) $-3 y$ C) $-21 y$

Multiple Choice

Simplify the expression.
- $-12 y+(-9 y)$

A) $-21 y^{2}$
B) $-3 y$
C) $-21 y$
D) $21 \mathrm{y}$