理工類英語考試練習小題
閱讀理解：
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.
The main idea of this paragraph is__________.
A.The Nature of Heavy Metals
B.Potential Hazards of Human Contaminated Soils
C.Heavy Metals and Food Chain
D.Research on Channels of Heavy Metals Getting into Human Food Chain
正確答案：B
答案解析：本段文字講的是：受到工業汙染的`土壤含有重金屬，而重金屬很穩定不容易降解，其中的某些微量重金屬能使人致癌或中毒。可以看出其中心內容是：受汙染土地的潛在危險，選擇B。