— Where is Mr. Wang?— He is not here. He must _______ the students’ papers in the office.

 Various efforts over the centuries _________ to predict earthquakes to reduce the damage. 

---Have you read the timetable ?   ---Yes .  The train ____ at 10:12 p.m..

By the time you have completed the essential training, you _____ exposed to virtually every new feature of the course．

—What do you think of the book?—Oh,great.It’s　　a second time.