Birth defects may be caused by a variety of environmental agents, called , which include some bacteria and viruses, various drugs and chemicals, and radiation.

the element that provides strength to the exoskeletons of clams and oysters is phosphorus. this is so because calcium carbonate is the main component in the shells.

explanation:

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.