There are many CD-ROMs in the bookshop. I don’t know ____ to buy.

We are disappointed why _______ few students could make _________ a wise decision.

—Both of the skirts are in style this year. —Yes, but I think the green one is           .

--There will be _____air pollution if there are_____ people driving. --I hope the air will be fresher soon.

The students are too _____ to keep their eyes open in class because of staying up late.