Question 15. ________ number of boys were swimming in the lake, but I didn’t know ________ exact number of them.

     A. A - the                      B. The - an                    C. The - the                   D. A - an

Question 16. It is imperative that this letter __________ immediately.

     A. is sent                       B. sends                        C. was sent                    D. be sent

18. Đề thi thử THPT 2021 - Tiếng Anh - Nhóm GV MGB - Đề 18 - có lời giải