“Where is Mother.” “She is in the kitchen. She _______ the housework all morning.”
A. is doing
B. was doing
C. has done
D. has been doing
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“What’s your opinion on the matter, please?” “Oh, sorry, I _______.”
A. wasn’t to listen
B. haven’t listened
C. wasn’t listening
D. hadn’t listened
“I suppose you _____ that report yet?” “I finished it yesterday, as a matter of fact.”
A. didn’t finish
B. haven’t finished
C. hadn’t finished
D. wasn’t finishing
2018U2-143 参与转录过程的酶是
A. DNA连接酶
B. 核酸内切酶
C. 引物酶
DNA聚合酶
E. RNA聚合酶
2018U2-144 仅在复制过程中合成短链RNA分子的酶是
A. DNA连接酶
B. 核酸内切酶
C. 引物酶
DNA聚合酶
E. RNA聚合酶
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