自考《英语（二）》真题练习：完成句子（1）

　　单选题

　　[完成句子]Heavy metals are persistent; they do not break down to other chemicals in the environment. Industrially polluted sites usually undergo intensive clean-up and rehabilitation because heavy metals are a health concern once they enter the food chain. Some trace metals are alleged to cause cancer and are also known to cause poisoning.

　　Industrially contaminated sites usually require a thorough clean-up due to __________.

　　A、the persistence of heavy metals

　　B、industrially polluted soils

　　C、naturally polluted soils

　　D、rock and soil chemistry

　　正确答案：A

　　答案解析：本段提到：受到污染的土壤含有重金属，而且重金属很稳定，不容易降解，所以要对重金属进行彻底的清除。答案选择A。

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