Find the Indicated Root, or State That the Expression Is $\sqrt [ 5 ] { - 1 }$

Multiple Choice

Find the indicated root, or state that the expression is not a real number.
- $\sqrt [ 5 ] { - 1 }$

A) $- \frac { 1 } { 5 }$
B) not a real number
C) 1
D) $- 1$