The unicellular biological active layer of a nematode is…

✅Explanation:

• The epidermis, also known as the hypodermis in nematodes, is the only unicellular and biologically active layer in their body wall. It is a single layer of cells located beneath the cuticle. The epidermis plays several crucial roles:
Secretes the Cuticle: The epidermis is responsible for producing and maintaining the tough outer cuticle.
Sensory Perception: It contains sensory receptors that help the nematode detect environmental stimuli.
Nutrient Absorption: In some nematodes, the epidermis is involved in nutrient absorption from the environment.