One winter day ____, he saw the tracks of animals in the snow and observed that the appearance of each one was different.

The prize of the game show is ＄30,000 and an all expenses _______ vacation to China．

We hurried to the station, _________ the train was gone.

Whom do you think Mary will _________ into the matter instead of her?   

As the film star began to appear，the children watched, ________.