Chinese paper was made from
A. the hair-like parts of certain plants.
B. the wood of trees.
C. the skin of certain young animals.
D. the stem Of tall plants.
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In 1900, the world's use of paper was about ______ for each person in a year.
A. 50 kilograms
B. I kilogram
C. 5 kilograms
D. 15 kilograms
种群平衡是指种群的出生率和死亡率相等。（）
A. 正确
B. 错误
二氧化碳和氮气都能直接参与植物的生理代谢。（）
A. 正确
B. 错误
You have to see these changes in______: they're part of a larger plan.
A. precedence
B. context
C. assortment
D. coverage
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