Simplify the Radical Expression $\sqrt [ 3 ] { 8 a ^ { 3 } }$

Simplify the radical expression. Assume a is unrestricted. $\sqrt [ 3 ] { 8 a ^ { 3 } }$

A) $2 a ^ { 3 }$
B) 8a
C) $8 a ^ { 3 }$
D) 2a
E) not real