Question

the great barrier reef, located near australia, is made up of over 2,000 individual coral reefs. thousands of different species of plants and animals live there. one explorer described the reef as “a wall of coral rock” in the ocean. this “wall” makes it difficult for ships to pass through. in fact, there have been at least 30 major shipwrecks there.
why is the word barrier a good word to include in the name of this reef?
it is made up of smaller coral reefs.
one explorer discovered large rocks there.
it is difficult to pass through.
many plants and animals live there.

Explanation:

The text states that the "wall" of coral rock makes it difficult for ships to pass through, which is characteristic of a barrier.

Answer:

C. It is difficult to pass through.