There is such a problem _________ we all should _________.
One winter day ____, he saw the tracks of animals in the snow and observed that the appearance of each one was different.
People from the West like to use these words in cases ____ some people in Asia may not think it necessary.
The manager would like to offer the position to ____ is fit for it.
I am sure ____ he did is wise.
By the time he ____ at the party, all the other guests ____ playing games.