For $$\frac{a}{b} < 1$$, define a * b $$= \frac{a}{b} + \frac{a^{3}}{b^{3}} + \frac{a^{5}}{b^{5}} + $$... then 4 * 6 =

A

$$\frac{1}{2}$$

B

$$\frac{2}{3}$$

C

1

D

$$\frac{6}{5}$$