Commensalism is when One species benefits and the other is harmed

Both species benefit

One species benefits and the other is not helped or harmed

Commensalism is a symbiotic relationship in which one species benefits while the other is not affected. Parasitism is a symbiotic relationship in which the parasitic species benefits while the host species is harmed.

The last one.

Explanation:

Had this on a test once. I got it right

answer; correlational;