You can try to guess the meaning of ______words you don’t know from ______ passage

I guess you can buy such a smart phone for 300 dollars—I could just two months ago，but the price ________ by 20%

Students can easily fall behind in their studies ____ they don’t manage their spare time carefully

People h____ the lack of water is the most seriousone.

Here are three books on history．Which one would you like to borrow— ______. You see，I’m interested in geography these days.