(2013·江西六所重点高中一模)We ________ take clean drinking water for granted. One day we may run out of it.

The World Wide Web is sometimes jokingly called the World Wide Wait because it ______ be very slow.

Now that the sign reads, “No person ______ smoke here”, please choose a seat in the smoking area over there if you _______ smoke.

I talked for a long time, and in the end I_____ make her believe me. 

 Surely Mr. Peterson ____ have forgotten to buy presents for his beloved family members. After all, it was Christmas!