US SCIENTISTS CLAIM THAT THEY _______ A NEW VACCINE AGAINST MALARI...

Lớp 11 Tiếng Anh TÀI LIỆU ÔN TẬP MÔN TIẾNG ANH LỚP 11 - TOPIC 1: GENERATION GAPS - ĐỖ BÌNH

18. US scientists claim that they _______ a new vaccine against malaria. A. developed B. have developed C. had developed D. was developing