A kind of population interaction in which one species benefits and the other is neither harmed nor benefited?

Commensalism

 The correct answer is Option (1) - Commensalism

Commensalism is an interaction in which one individual benefits while the other is neither helped nor harmed. For example, orchids (examples of epiphytes) found in tropical rainforests grow on the branches of trees in order to access light, but the presence of the orchids does not affect the trees. Commensalism can be difficult to identify because the individual that benefits may have indirect effects on the other individual that are not readily noticeable or detectable.

The cattle egret and grazing cattle in close association, is a classic example of commensalism. The egrets always forage close to where the cattle are grazing because the cattle, as they move, stir up and flush out insects from the vegetation that otherwise might be difficult for the egrets to find and catch.

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.