Explanation:

- The earthworm is moving at a speed of 4 cm/s.

- The insect overtakes the earthworm in 6 seconds.

- To find the insect's speed, calculate how much further it travels in those 6 seconds.

- During 6 seconds, the earthworm covers $4\text{cm/s}\times 6\text{s}=24\text{cm}$.

- The insect must cover at least 24 cm more than the earthworm to overtake it.

- Insect's relative speed: $\frac{24\text{cm}}{6\text{s}}=4\text{cm/s}$.

- Total insect speed: $4\text{cm/s}+4\text{cm/s}=8\text{cm/s}$.

- Correct Answer: None of the provided options are accurate.