As nobody here knows what is wrong with the machine, we ________send for an engineer to handle the problem.
Some students often listen to music __________ classes to refresh themselves.
— __________ when has the country been open to international trade? — 1978, I suppose.
— I think he is taking an active part in social work. —I agree with you __________.
I have offered to paint the house __________ a week’s accommodation.
I _____ you yesterday, but you weren’t in.