What's a cone of depression? O A. An area where one cave
connects to another cave
O B. An area where a cave collapses
in on itself
O C. An area where the water table
slopes toward a well
O D. An area where surface water
reaches an aquifer

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. calcium carbonate is strengthened by phosphorus.

explanation:

nucleus

would be most reasonable answer tbh