2010-12-6——One question per day

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This post was last edited by yzhang2010 on 2011-8-4 at 15:25. 1. The **standard for water scarcity** is that the annual freshwater supply per person should be below A. 1000 T B. 1700 T C. 2000 T D. 3000 T. 2. Which of the following is the most important foundation for maintaining the material and energy cycles in the biosphere as well as protecting the ecosystem? A. Rivers B. Mountains C. Forests D. Land. 3. The area of land degraded by desertification worldwide accounts for A. 1/2 of the world’s total land area B. 1/3 C. 1/4 D. 1/5. 5. The bridge that connects natural sciences and social sciences is A. Ecology B. Human ecology C. Philosophy D. Economics. 6. Biological resources such as plants, animals, and microorganisms belong to A. Primary natural resources B. Renewable resources C. Non-renewable resources D. Uncertain. Answers: B C C A A