Evaluate the Radical Expression If It Is a Real Number $- \sqrt { 64 }$

Evaluate the radical expression if it is a real number. Use a calculator to approximate irrational numbers to the nearest
hundredth. If the expression is not a real number, so state.
- $- \sqrt { 64 }$

A) -4096
B) -8
C) $\frac { 1 } { 64 }$
D) not a real number