A thick walled hollow sphere has outer radius R. It rolls down an inclined plane without slipping and its speed at bottom is v₀. Now the incline is waxed so that the friction becomes zero. The sphere is observed to slide down without rolling and the speed now is (5 v₀/4). The radius of gyration of the hollow sphere about the axis through its centre is
A. 3R/4
B. R/2
C. R/4
D. 4/5 R