Explanation:

- The earthworm is 18 cm long and moves at 4 cm/s.

- The insect overtakes (i.e., covers the full length of the earthworm) in 6 seconds.

- In 6 seconds, the earthworm moves 4 x 6 = 24 cm.

- To overtake, the insect must cover the 18 cm length of the worm in addition to whatever the earthworm has moved in these 6 seconds, i.e., 18 cm + 24 cm = 42 cm.

- So, the speed of the insect = 42 cm / 6 s = 7 cm/s.

Option:1, 7.0 cm/s is correct.