One species benefits and the other is unaffected.

• A. Symbiosis
• B. Niche
• C. Commensalism
• D. Competition

Answer: (C)

This describes commensalism, a type of association where one species benefits while the other is largely unaffected. A classic example is remoras hitching a ride on sharks: the remora gains transport and access to scraps, while the shark isn’t helped or harmed in any meaningful way.

Symbiosis is a broad umbrella term for close ecological relationships and includes several kinds, not just this one. A niche is about the role and position of a species in an ecosystem, not a relationship between two species. Competition involves both parties trying to use the same limited resources, usually with negative effects for at least one participant, not one benefiting and the other remaining unaffected.