—Are these books ____?—No, they are not his. They belong to ____.

It’s impossible to get good _____ without hard work. 

 －How many _____ are there in the box？－Oh, there’re four.

 Please pick up the _______. Don’t keep it on the floor.

-You look so worried, what’s wrong?  -More and more people like me begin to worry about the ______ pollution after the haze (雾霾) appeared in Beijing and some other cities in China.