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问题 单项选择题

厂区被SO2轻度污染时，通过柳杉、丁香等植物吸收SO2可消除污染，这表明生态系统具有（）

A.恢复力稳定性

B.抵抗力稳定性

C.反馈调节

D.无限的自动调节能力

答案

参考答案：B

单项选择题

Specific duties are levied（）some physical unit such as dollars per bushel, per kilo, or per metre and ad valorem duties are calculated as a percent of the value of the goods.

A. on the basis of

B. with the basis of

C. on the base of

D. with the base of
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