Answer:
D. Commensalism
Step-by-step explanation:
The relationship between a remora and a shark is an example of commensalism - it's good for one side but neither good nor bad for the other. The remora attaches itself to the shark and gets the benefit of eating the shark's leftovers, but there is no harm or benefit for the shark, and the shark doesn't eat the remora like in a predator/prey relationship.