Identify the commensalism from the following associations:

The correct answer is Option (4) → Sea anemone and clown fish

Commensalism is an interaction in which one species benefits and the other is neither harmed nor benefited (+, 0).

Option (1) Fungi and roots of higher plants. — Incorrect. This is mycorrhiza, a case of mutualism: the fungus helps the plant absorb nutrients and the plant gives it carbohydrates.

Option (2) Cuckoo and crow during breeding season — Incorrect. This is brood parasitism: the cuckoo lays its eggs in the crow's nest and the crow raises the cuckoo's young at its own cost.

Option (3) Fig species and wasp — Incorrect. This is mutualism: the wasp pollinates the fig, and the fig gives the wasp a place to lay eggs and food for its larvae.

Option (4) Sea anemone and clown fish — Correct. In commensalism one species benefits and the other is neither harmed nor benefited (+/0). The clown fish living among the stinging tentacles of the sea anemone gets protection from predators, and the anemone does not appear to gain anything.

NCERT Extract:
Population Interactions – “… Another example of commensalism is the interaction between sea anemone that has stinging tentacles and the clown fish that lives among them. The fish gets protection from predators which stay away from the stinging tentacles. The anemone does not appear to derive any benefit by hosting the clown fish.”