Zhengzhou was attacked by such a terrible sandstorm ________ few residents had ever experienced before.
The children were warned of not being too _______ about things you are not supposed to know.
Americans eat____ vegetables per person today as they did in 1990.
Students ______ remain in their seats until all the exam papers have been collected.
The atmosphere of the earth ______ us from the strong sun light.
---How well did John do in the match? --Wonderful. I think we can’t have a ______ player in our football team.