You should try to avoid _________ the same mistake over and over again.

The price system is a complex network composed ofthe prices of all the products bought and sold in the economy as well as ofa great number of services.

Is this the reason ______ at the meeting for hiscarelessness in his work

It’s said that within five years cars will be a lot ____in our country.

Some of this heat near the earth’s surface_________ make electricity.