$$\frac{8}{3}, \frac{25}{12}, \frac{5}{9}$$, ______, $$\frac{32}{21}, \frac{81}{56}$$

A

$$\frac{24}{18}$$

B

$$\frac{49}{30}$$

C

$$\frac{23}{18}$$

D

$$\frac{25}{18}$$