Since the introduction of the new technique, the production cost____ greatly.
A. reduces
B. reduced
C. is reducing
D. has been reduced
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By the time you get there tomorrow, they___ for Beijing.
A. will have left
B. are leaving
C. will leave e
D. are to leave
A young man stood nearby while I (read) ______the newspaper.
There (be) _____ several such occurrences in the past few weeks.
Look, the cat (run) ____ after the mouse.