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Mr.Grunfeld______ for his humour already, but on this occasion the whole class_____ hysterically.
A. knew - had been laughing.
B.was known - laugh
C. Has known - laughed
D. Is known - was laughing
Câu nào đúng thì giải thích cho em hiểu vì sao lại chọn câu đó.
A. knew - had been laughing.
B.was known - laugh
C. Has known - laughed
D. Is known - was laughing
Câu nào đúng thì giải thích cho em hiểu vì sao lại chọn câu đó.