Question

how do coral reefs form?
a reef is made of living things. various species of coral have different shapes.
each coral is a group of tiny animals called polyps. polyps have long, arm - like
parts called tentacles. they capture prey with them. many coral species
release calcium carbonate. this compound hardens and forms an
exoskeleton around the polyp. a coral reef forms when the skeletons of many
coral join together. the reef expands as older coral die. the skeletons left
behind are a safe place where young coral attach and grow.
the reefs beautiful colors are not from the coral but from algae living within

question 5
which passage from the article best supports the idea that acidity
harms coral reefs?
a. polyps have long, arm - like parts called tentacles. they
capture prey with them.
b. rising ocean acidity stems from burning fossil fuels like
gasoline.
c. acidic seawater dissolves calcium carbonate polyps use to
make skeletal shells.
d. carbon dioxide and seawater react to produce an acid.
this increases ocean acidity.

Explanation:

The question asks which passage from the article best supports the idea that acidity harms coral reefs. Option C mentions that acidic seawater dissolves calcium carbonate (which polyps use for skeletal shells). Calcium carbonate is crucial for coral reef structure. Acidic conditions (related to acidity) breaking down this material directly shows how acidity harms coral reefs. Options A and B do not relate to acidity. Option D explains the cause of increased ocean acidity (carbon dioxide - seawater reaction) but does not directly show how acidity harms coral reefs like Option C does.

Answer:

C. Acidic seawater dissolves calcium carbonate polyps use to make skeletal shells.