The man kept silent in the room unless ______ .
A. spoken to
B. spoke to
C. spoken
D. to speak
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He was often listened ______ in the next room.
A. sing
B. sung
C. to sing
D. to to sing
What’s troubling them is ______ enough experienced workers.
A. that they have to
B. they have not
C. their not having
D. not their having
_____ his telephone number,she had some difficulty getting in touch with Bill.
A. Not knowing
B. Knowing not
C. Not having known
D. Having not know
Bamboo is used ______ houses in some places .
A. to build
B. to building
C. to be built
D. being built
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