Jack, look! Everybody is doing homework quietly. ______ you make a noise in class?
Having a trip abroad is certainly good for the old couple, but it remains _______ whether they will enjoy it.
_______ such heavy pollution already, it may now be too late to clean up the river.
Robert is said _______ abroad, but I don’t know what country he studied in.
The purpose of new technologies is to make life easier, _______ it more difficult.
When I got back home I saw a message pinned to the door _______ “Sorry to miss you; will call later.”