what is the torque required to produce the same angle of twist?

Question

In power transmission shafts if the polar moment of inertia of a shaft is doubled then what is the torque required to produce the same angle of twist?                 

(a) $\frac{1}{4}$ of the original value

(b) $\frac{1}{2}$ of the original value

(c) Same as the original value

(d) Double the original value