Simple harmonic motion

i checked

option a is correct

"vertical axis of symmetry "

it is not mention in the question, where is the center of axis..

i take r=L/2 because axis of rotation is at the center of rod .. but if the center of axis is at one mass then r=L..

solution is attached..option c is correct... forces on a mass when it is rotating is tension and centripetal force. rod don't breaks so that both forces on masses must be equal...