单选题：To protect our ecosystems we should not use more than_______

题目分类：理工类
题目类型：单选题
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题目内容：

To protect our ecosystems we should not use more than_______ A．our share of resources
B．a biological creature
C．a given area
D．the maintenance of the ecosystem
E．the source of food
F．various species

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分类：理工类题型：单选题

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