wonder how it ________ that they made such rapid progress.

People have lots of problems living in the central Australian desert, ____ the lack of water is the most serious one

Why didn’t you tell him about the meeting?—He rushed out of the room____ I could say a word.[ ]

______ is a waste of time spending many hours ______ computer games every day.

My classmate Frank is better __________than the others in my class.