山东自学考试-00015英语二每日一练12.19

1、【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。