Spider Crabs Live on the Ocean Floor in Shallow Areas

Spider crabs live on the ocean floor in shallow areas and greenish-brown algae live on their backs. This provides the algae with a home and the algae's greenish-brown color helps the crab blend in and stay safe from predators. This association can be considered a mutualism because

A) both partners receive a net benefit.
B) the association is an altruistic one.
C) one partner benefits and the other is not harmed.
D) the crab obtains a greater net benefit than the algae.