• A. industrially polluted soils
• B. rock and soil chemistry
• C. naturally polluted soils
• D. the pathways of metals into the food chain
• E. the element of iodine
• F. the persistence of heavy metals

It is extremely necessary to study the long-term effects caused by living on ______.

A．By measuring the seismic waves caused by rocks’ pushing together.
B．By observing animal’s behaviors.
C．By recording the changes of astronomical phenomena
D．Not mentioned