A lizard, at an initial distance of 21 cm behind an insect, moves from rest with an acceleration of $2\; cm/s^2$ and pursues the insect which is crawling uniformly along a straight line at a speed of 20 cm/s. The the lizard will catch the insect after :

Question

( A ) 24 s
( B ) 21 s
( C ) 1 s
( D ) 20 s