Try ______ the back door if nobody hears you at the front door.
A. to knock at
B. knock at
C. knocking at
D. knocked at
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These language points deserve _______.
A. to mention
B. mention
C. mentioned
D. mentioning
They don’t allow ________ in the library, but they allow people ______in the restroom.
A. to smoke…to smoke
B. to smoke…smoking
C. smoking…smoking
D. smoking…to smoke
It is no use ____ me not to worry.
A. you tell
B. your telling
C. for you to have told
D. having told
He is very busy ____ his papers. He is far too busy ____ callers.
A. to write...to receive
B. writing...to receive
C. writing...receiving
D. to write...for receiving
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