If we put $$\frac{7}{9}, \frac{6}{8}, \frac{5}{6}, \frac{4}{5}$$ in desending order, then the difference between first and second number is

A

$$\frac{1}{36}$$

B

$$\frac{1}{12}$$

C

$$\frac{1}{30}$$

D

$$\frac{1}{24}$$