發(fā)布時間: 2016年03月11日
概括大意與完成句子
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
【正確答案】 A
【答案解析】 本段提到:受到污染的土壤含有重金屬,而且重金屬很穩(wěn)定,不容易降解,所以要對重金屬進行徹底的清除。答案選擇A。