The question that puzzled them is ____ they can get rid of the air pollution in the area.
The trip was hard at first. But it was smooth_____ .
As is known to all, the financial crisis firstly broke out in the United States,_____ the group of developed countries.
Zhang Yining has trained continuously for six hours. _____ she is tired out.
Mr Smith never does any reading in the evening;____ .
It is useless to argue with him. You might just____ go to the seaside to argue with the sea.