Choose the correct answer to each of the following questions.

Câu hỏi

Much progress in telecommunications _during World War I, but the basic technique_in the previous decades.

A. was achieved - had been developed

B. has been achieved - were developed

C. had been achieved - has been developed

D. would have been achieved - were developing

Đáp án
A. was achieved - had been developed

Câu hỏi thuộc Bài tập:

Chuyên đề ôn thi: Thì của động từ (3)