This kind of cancer can be cured, provided it is ______ early.
—Why do you look sad?—There are so many problems ________.
A few days after the interview,I recevied a letter ________ me admission to the university.
—We didn't find the Blacks ________ the lecture.—No one had told him about ________ a lecture the following day.
Only ________ according to the directions can the medicine be quite effective.
The man we followed suddenly stopped and looked as if ________ whether he was going in the right direction.