During an adiabatic process, if the pressure of a gas is found to be proportional to the cube of its absolute temperature, then the ratio of $$\frac{C_P}{C_V}$$ for the gas is :

A

$$\frac{5}{3}$$

B

$$\frac{9}{7}$$

C

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

D

$$\frac{7}{5}$$