Pick the odd one out $\large\frac{6}{216}, \frac{4}{64}, \frac{8}{516}, \frac{9}{729}$

Question

$( A ) \large\frac{8}{516} \\ ( B ) \large\frac{9}{729} \\ ( C) \large\frac{4}{64} \\ (D)\large\frac{6}{216} $