A stationary horizontal disc is free to rotate about its axis. When a torque is applied on it, its kinetic energy as a function of θ, where θ is the angle by which is has rotated, is given as kθ^{2} . If its moment of inertia is I then the angular acceleration of the disc is

(1) k/I θ

(2) k/2I θ

(3) k/4I θ

(4) 2k/I θ