The overgrowth of plankton and algae threaten the existence of . A.
seaweed
B.
sandstone
C.
coral reefs
D.
undersea caves

Please select the best answer from the choices provided

A
B
C
D

C

Explanation:

coral reefs

Explanation:

d. i assume the underlined word is "role." reformat if it isn't.

explanation:

role is closest to part because when replacing words, "playing a vital decision," "playing a vital activity," and "playing a vital dollar" don't make logical sense. the only meaningful choice is "playing a vital part."

this fits one of merriam-webster's definitions of role: "a function or part performed especially in a particular operation or process."

answer; all of the answers are correct;