I have no idea what ____ while I was asleep.
A. has happened
B. was happened
C. had happened
D. happened
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I ___ so busily recently that I ______ no time to help you with your math. That’s OK. I can manage it by myself.
A. have been working; have
B. have worked; had
C. am working; will have
D. had been working; had had
He ____ at the meeting, but his heart attack prevented him.
A. will speak
B. is going to speak
C. had to speak
D. was going to speak
I ____ ping-pong quite well, but I haven’t had time to play since the New Year.
A. will play
B. have played
C. played
D. play
翻译的产物是
A. 戊糖
B. 核酸
C. 蛋白质
D. 氨基酸
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