单选题
[概括大意]So far there is no data to suggest that people living on metal-rich soils experience a potential health hazard. The levels of metals within naturally contaminated soils are generally not high enough to cause serious health problems. Living on metal-rich soils does not represent a health risk unless large quantities of soil are digested or metal-rich dust is inhaled. However， small children are particularly exposed to metal-rich topsoil in playgrounds and gardens. They are also the most likely ones to eat potentially dangerous metal-rich soil.
The main idea of this paragraph is__________.
A.Potential Hazards of Human Contaminated Soils
B.Research on Channels of Heavy Metals Getting into Human Food Chain
C.Long- term Health Effects on Health Problems
D.No Evidence to Indicate Bad Effects of Naturally Contaminated Soil
正确答案：B
答案解析：本段文字涉及到的是自然污染的土壤一般情况下对人体不会造成危害，首句So far there is no data to suggest that people living on metal-rich soils experience a potential health hazard.便提示出这一点，而D选项只是这个句子的同义转述。