It can be inferred from the passage that limestone deposits serve as the basis of ...........
A. coral reefs
B. red algae
C. subtropical seawater
D. secret passages
* Đáp án
A
* Hướng dẫn giải
Đáp án A Thông tin ở câu cuối của bài: This type of algae has an essential role in the formation of coral reefs: it secretes lime from the seawater to foster the formation of limestone deposits.