There is no doubt _______ nearsightedness is a serious problem among the youth of our country.

The notice came around two in the afternoon _____ the meeting would be put off.

_____ great progress we have made, we should not be conceited.(自大的)

It was at midnight ______ he got to his friend’s house． 

The man was walking along the street        he stopped and looked as if                   whether he was going in the right direction.