Pea crabs live their entire lives inside of an oyster. They live inside the oyster's gills and feed on the food that filters in. Often as the oyster grows, its muscles and gills will become weak. This symbiotic
relationship is an example of
O Parasitism
O Predation
O Mutualism
O Commensalism

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.

the electromagnetic energy from the sun arrives in the form of visible and invisible light.