A relationship in which one organism is benefited while other is neither benefited nor harmed is known as
Commensalism is a type of interaction among two organisms where one organism is benefited whereas other remains unaffected (neither harmed nor benefited). The common example of commensalism is Barnacles which are sessile and does not move by its own, they get attached to the sides of whales and in turns transport to different places which helps them in feeding. Barnacles are benefited because of this association whereas whales remains unaffected. Thus, the correct answer is option A.