Mutualism is the association between two species in which both of them are benefited from their association. Therefore, option (a) is incorrect.
Parasitism is an association in which out of the two species that involve in the association, one species is benefited whereas the other one is harmed. The species that is benefitted exploits the other organism as resource for its benefit. Therefore, option (b) is incorrect.
Competition is the process in which organisms of same or different species compete with each other for the available resources. Therefore, option (c) is incorrect.
Commensalism is an interaction between the individuals of different species in which only one partner is benefited but the other one is neither benefited nor harmed. Therefore, option (d) is correct.
Hence, a relationship in which one organism is helped and other organism is neither helped nor hurt is called (d) commensalism.