By the end of thiscentury, scientists ______ a cure for the common cold.
A. must discover
B. must have discovered
C. will have discovered
D. would discover
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Mr. Smith _______with the government for 40 years by the time he retired.
A. would have worked
B. has worked
C. could have worked
D. had worked
He will come to see you the moment he _______ his work.
A. finishes
B. had finished
C. would finished
D. will finish
Do not disturb me. I_______ letters all morning and have written ten so far.
A. have been writing
B. have written
C. am writing
D. was writing
This is the third time we _______ improvements in that equipment.
A. are making
B. made
C. have made
D. will make
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