Nancy offers to pay Jennifer $250 if Jennifer will paint her apartment while she is out of town on vacation for two weeks. Jennifer makes no promise but tells Nancy that she will think about it. While Nancy is out of town, Jennifer paints the apartment. This is best described as a(n):

Often, a goby fish and a shrimp will live together in a burrow the shrimp has dug in the sand. the shrimp is almost blind and therefore is unable to see predators approaching when he is outside of the burrow. when the shrimp is in danger, the goby fish touches the shrimp with its tail to warn him. then, both go back into their burrow for safety. which type of relationship does this represent? a. mutualism b. parasitism c. commensalism d. predator/prey