Ex2. Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

Câu hỏi

The engineers _____ this system daily since they introduced it last year.

A. used

B. use

C. had used

D. have used

Đáp án
D. have used

Câu hỏi thuộc Bài tập:

ENGLISH 9- 26/12/2025