A string passing over a smooth pulley carries a stone at one end. While its other end is attached to a vibrating tuning fork and the string vibrates forming 8 loops. When the stone is immersed in water 10 loops are formed. The specific gravity of the stone is close to<br /> <br />A)  1.8<br />B)  4.2<br />C)  2.8<br />D)  3.2