How does the clown fish benefit from living among sea anemones?

The correct answer is Option (2) → Protection from predators due to the anemone's stinging tentacles

The clown fish lives among the stinging tentacles of the sea anemone. Predators keep away from the tentacles, so the fish is safe there. The anemone does not seem to gain anything. When one species benefits and the other is neither harmed nor helped, the interaction is commensalism.

Option (1) Access to food provided by the anemone — Incorrect. The anemone does not feed the clown fish. The book names only protection as the fish’s benefit.

Option (2) Protection from predators due to the anemone's stinging tentacles — Correct. Predators avoid the stinging tentacles, so the clown fish living among them gets protection from predators.

Option (3) Mutualistic relationship with the anemone — Incorrect. In mutualism both species benefit, as in lichens or mycorrhizae. Here the anemone derives no benefit, so the relationship is commensalism, not mutualism. This option also names a type of interaction, not a benefit.

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.”