Ithink it might be c.

cells in the phase of the cell cycle can no longer undergo mitosis.

a. g0 phase
b. s1 phase
c. g1 phase
d. s phase

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:

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.