连续精馏操作时,若进料液汽比为1:4(摩尔)时,则进料热状况参数q为()。
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He English for 3 years before he came here .
A. is still learning
B. had been learning
C. was still learning
D. has been learning
Han Mei told me she _____lunch, so she was very hungry.
A. has had
B. hasn't have
C. have had
D. hadn't had
By the end of 1976, many buildings _____built in the city.
A. have been
B. have
C. had been
D. will
They on the program for almost one week before i joined them, and now we on it as no good results have come out so far.
A. had been working; are still working
B. had worked; were still working
C. have been working; have worked
D. have worked; are still working