Use the Associative Property to Rewrite the Expression, and Then $\frac{1}{7}(6 a)$

Multiple Choice

Use the associative property to rewrite the expression, and then simplify the result. $\frac{1}{7}(6 a)$

A) $42 a$
B) $13 a$
C) $\frac{1}{13} a$
D) $\frac{6}{7} a$
E) $\frac{7}{6} a$