Safety in school has been of great concern because of frequent reports about accidents _______ students got injured or killed while in school .

________ do you clean your kitchen?- Twice a week.[ ]

_____ do you see your grandparents?— Once a month.[ ]

Here is the knife. You can ask your mother ___the apple for you.

About 20 firemen were killed in the fire which broke ______in Yueyang, Hunan Province last week.[ ]