Simplify the Exponential Expression $$64 ^ { - 4 / 3 }$$

Multiple Choice

Simplify the exponential expression. Write any negative exponents as positive exponents. Assume all variables represent positive real numbers.
- $$64 ^ { - 4 / 3 }$$

A) 256
B) not a real number
C) $\frac { 1 } { 256 }$
D) $- \frac { 1 } { 256 }$