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.
A number of special conditions is necessary for the formation of a geyser.
A. special
B. is
C. for
D. formation
A number of special conditions is necessary for the formation of a geyser.
A. special
B. is
C. for
D. formation
are - Động từ chia theo danh từ sau cụm A number of
Đáp án B.