Simplify the Expression $\frac { a ^ { 3 / 7 } a ^ { 2 / 7 } } { a ^ { 1 / 7 } }$

Multiple Choice

Simplify the expression. $\frac { a ^ { 3 / 7 } a ^ { 2 / 7 } } { a ^ { 1 / 7 } }$ Write all answers without using negative exponents.Assume that all variables represent positive numbers.

A) $\quad a ^ { 4 / 10 }$
B) $\quad a ^ { 6 / 7 }$
C) $\quad a ^ { 4 / 14 }$
D) $\quad a ^ { 4 / 7 }$
E) $\quad a ^ { 5 / 7 }$