In a word, we live without plants.

What do you think of math—- I think it’s useful, so it’s ______ for us to learn it well.

Which of the two magazines will you take– I’ll take ____ though I find ____ of them are useful to me.

How can I wake up so early — Set the alarm at 5:00 am ________ youwill make it

Tom ________ in the library every night over the last three months．[ ]