It is required in the library regulations that any book borrowed __________ by due time, or the borrower will be fined.
21.The moment we heard the news of the earthquake, we began to ________ the work to rescue those who were trapped in the building.
20. When Jane began to take swimming lessons, her main__________was the fear of water.
19. The language used in advertisements differs from____________used in ordinary readings.
18._________is often the case, he didn’t study hard and failed to pass the test.
17.They had a pleasant chat____________a cup of coffee.