Choose the word/expression which best completes each sentence :

It is time we ....

Choose the word/expression which best completes each sentence :
He sent the children out to play .... he might be alone.

Choose the word/expression which best completes each sentence :
He played the piano .... an hour or two

Choose the word/expression which best completes each sentence :
The solution to the problem has so far .... the scientist

Choose the word/expression which best completes each sentence :

The teacher asked if she .... seen her boyfriend recently