單項(xiàng)選擇題

Silk（）by Chinese for thousands of years now.

A.has used
B.has been used
C.was used
D.is used

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單項(xiàng)選擇題

By the end of this year, I（）enough money for a holiday

A.will save
B.will be saving
C.will have saved
D.will be saved

單項(xiàng)選擇題

By next year he（）in New York for five years.

A.has worked
B.has been working
C.works
D.will have worked