Simplify the Expression $- 3 z ^ { - 2 }$

Multiple Choice

Simplify the expression. Write the result using positive exponents only.
- $- 3 z ^ { - 2 }$

A) $\frac { 9 } { z ^ { 2 } }$
B) $- \frac { 1 } { 9 z ^ { 2 } }$
C) $\frac { 1 } { 9 z ^ { 2 } }$
D) $- \frac { 3 } { \mathrm { z } ^ { 2 } }$