Why are shellfish populations often a good indicator of water quality? a. many shellfish are filter feeders that absorb toxins from the water b. many shellfish are herbivors, and reduce vegetation overgrowth c. many shellfish are photosynthesizers, and add oxygen to the water d. many shellfish are predators, and reduce the number of waste-creating fish

 the final answer is A

A. many shellfish are filter feeders that absorb toxins from the water is the correct answer.

Explanation:

shellfish are filter feeders. shellfish filter water by absorbing particles and toxins present in the water, they maintain the water quality by pumping the water with the help of their cilia that cover their gills.Shellfish need a large amount of dissolved oxygen and their excess is a sign of the good quality of water.There are different types of shellfish such as crab, clams, oysters, crayfish, and mussels.

thus option(A)  many shellfish are filter feeders that absorb toxins from the water is the correct answer.

The diaphragm is what i think ur talking about