Torque, Tis applied at the free end of a stepped rod of circular cross-section as shown in figure. If the shear modulus of the material is G, the angular twist, $$\theta$$ at free end will be

A

$$\frac{12 TL}{G \pi d^4}$$

B

$$\frac{24 TL}{G \pi d^4}$$

C

$$\frac{36 TL}{G \pi d^4}$$

D

$$\frac{48 TL}{G \pi d^4}$$