Plzz expain above givn question.from rotational motion

Correct answer​ is option a. 

Solution-> assume one mass to be bigger, suppose M1.let total length of rod be L. Let M1 to be at the origin and find the position of centre of mass of the rod. It will come out to be m2L/ M1+M2 along x-axis . Let the C.o.m lie x distance from origin. So distance of M2 from c.o.m will be L-x.

Finding moment of inertia now, we get this equation = I = m1r1^2 + m2r2^2

                                                                                                   =  m1x^2 + M2(L-x)^2

              Substitute x=m2L/M1+M2

And you will get the desired equation = m1m2 × L^2/M1+m2