Right option is (a) 2s

The explanation is: The kinetic energy of a particle in SHM is given by:

0.5mA^2w^2cos^2(wt + a), where a is the phase constant.

cos^2(wt + a) = (1 + cos2(wt+a))/2.

Therefore the time period of oscillation of kinetic energy is 4/2 = 2s.