You had better ________ some time every day for sports so that you can keep yourself energetic.

______in bed will do harm _______ your eyesight

If you don’t work hard for most of the year and then work hard for only a few days before the exam, you will probably     .

In ancient times, dogs were mainly ______helping people hunt( 打猎) .Now they are more useful-they can help the blinds, search for the bad eggs.

—_____ swim in the river? — oh, no. Our teacher told us ____ here. It’s dangerous.