Students often ______ a lot of difficulties when they communicate with foreigners for the first time.

You can go out, _________ you promise to be backbefore 11 o’clock.

Some of the rubbish, such as wood, paper and iron,_____ away over a long period of time.

Walking alone in the dark, the boy whistled to________ his courage. [ ]

________ have you kept the book —Since last Month. I ____ return it to the library today or I can’t borrow one next time.