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Students should be encouraged to use _________ Internet as _________ resource.

Paper money was in ____ use in China when Marco Polo visited the country in ____ thirteenth century.

There is no easy walk to __________ freedom anywhere，and many of us will have to pass through __________ valley of the shadow of death again and again before we reach the mountaintop of our desires．

As environment protection is becoming _______ public concern, _______ government is determined to pay more attention to the issue.

Sun Yang,＿Olympic and world swimming champion of China, has received＿ indefinite ban from competition following his seven-day detention for driving without a license.

The development of industry has been ____gradual process throughout _____ human existence, from stone tools to modern technology.

John, _______ university professor, is considered to be _______ success as ______ expert in the agriculture research.

—He has a lot of friends who have a lot in ________ common with himself.
—Indeed.Birds of ________ feather flock together.

(2013·豫北三校聯(lián)考)Friendship is both ________ source of pleasure and ________ component of good health.

We can never expect ________ bluer sky unless we create ________ less polluted world.(2009·安徽)