Mark the letter A, B, C, or D on...

Câu hỏi: Mark the letter A, B, C, or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.
Of the more than 1,300 volcanoes (A) in the world, only (B) about 600 can classify (C) asactive (D) ones.

A. volcanoes

B. only

C. classify

D. asactive