An observer can wee through a pinhole the top end of a thin rod of height h, placed as shown in the figure. The beaker height is 3h and its radius h. When the beaker is filled with a liquid up to a height 2h, he can see the lower end of the rod. Then the refractive index of the liquid is
(a) 5/2
(b) √(5/2)
(c) √(3/2)
(d) 3/2
