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Câu hỏi: Mark the letter A, B, C or D to indicate the correct answer to each of the following questions.
____ his homework, he started to surf the social networks.
A. At the time he finished
B. After he has finished
C. After he had finished
D. By the time he finishes
____ his homework, he started to surf the social networks.
A. At the time he finished
B. After he has finished
C. After he had finished
D. By the time he finishes
Vì mệnh đề chính chia ở quá khứ đơn, nên mệnh đề phụ chia ở quá khứ => loại B, D
A. At the time + quá khứ, S + Vqua khứ tiếp diễn => Sai
A. At the time + quá khứ, S + Vqua khứ tiếp diễn => Sai
Đáp án C.