In a specimen-based viva, the examiner describes this case: an earthworm must keep its skin moist to exchange gases effectively. Choose the concept that fits it best.

Earthworms exchange gases through their moist body surface, a process called cutaneous respiration. Dry skin reduces diffusion and can be fatal. This MCQ belongs to the Annelida topic in Animal Diversity-I and is written to test concept understanding rather than memorized wording.