Write in Exponential Form $\sqrt [ 7 ] { x ^ { 4 } }$

Multiple Choice

Write in exponential form. Assume all variables are positive real numbers.
- $\sqrt [ 7 ] { x ^ { 4 } }$

A) $x ^ { 7 / 4 }$
B) $x ^ { 4 / 28 }$
C) $x ^ { 4 / 7 }$
D) $x ^ { 1 / 28 }$