If $$\frac{a}{b}=\frac{b}{c}=\frac{c}{d} ,then\frac{a}{d}$$ in terms of b and c is equal to:

A

$$(\frac{b}{c})^{3}$$

B

$$(\frac{b}{c})^{2}$$

C

$$(\frac{b}{c})^{1.5}$$

D

$$(\frac{b}{c})^{0.5}$$