Knowing how long the test would last, the students who finished ____ back and waited until the end of the exam.
_________ the project in time, the workers were working at weekends.
_________ many times, he finally understood it.
The chairman thought _________ necessary to invite Professor Smith to speak at the meeting.
It was not until nearly a month later _________I received the managers reply.
---- What do you think of the book? ---- Oh, excellent .It is worth __________ a second time.