概括大意与完成句子

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.

KET线上班

6-12岁英语高频重点词汇，搞定小学英语全段考试

399查看

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。

阅读推荐：职称英语培训 学派网职称英语 新东方职称英语 环球网校职称英语