There are a number of empty __________.

Jim is _____ .   

-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. 

Everyone needs at least eight _________ sleep a night. ——I agree. 

When I hurriedly got to the airport ,the lady at the window told me that there were no________ left on the plane.