Someone is ringing the doorbell. Go and see ______.
It was not until he came back _____ he knew the police were looking for him.
All her time _______ experiments, she has no time for films.
Some students are now busy preparing for the “Independent Recruitment(自主招生)” contest, in hopes of getting a “Pass” card at their first _______.
While income worry is _______ rather common problem of the aged, loneliness is another problem that _______ aged parents may face.
-So you gave Mary your dictionary?-______.She said she'd return it to me when she could afford her own.