Simplify the Following by Combining Like Terms $- 8 m ^ { 3 } + 5 m ^ { 3 }$

Multiple Choice

Simplify the following by combining like terms.
- $- 8 m ^ { 3 } + 5 m ^ { 3 }$

A) $- 9 \mathrm {~m}$
B) $- 3 m ^ { 3 }$
C) $- 3 m ^ { 6 }$
D) cannot be simplified