A man throws ball with the same speed vertically upwards one after the other at an interval of 2 seconds. What should be the speed of the throw so that more than two balls are in the sky at any time ? (Given $g = 9.8 m/s^2$)

Question

( A ) Any speed less than 19.6 m/s
( B ) At least 9.8 m/s
( C ) More than 19.6 m/s
( D ) Only with speed 19.6 m/s