We ______ a new experiment this afternoon.
A. shall be to perform
B. will be to perform
C. are to be performed
D. are to perform
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You ought to _____ a test in physics the day before, I think.
A. have taken
B. take
C. be taken
D. be taking
Kepler proved that the sun ______ the center of the solar system.
A. is
B. was
C. had been
D. would be
This is one of the best novels that ______ this year.
A. appears
B. is appearing
C. has appeared
D. have appeared
My friend ______ here last week, but he couldn’t.
A. was to have come
B. must have come
C. came
D. had to come
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