Most rainforest soils are thin and poor because （　　）．

A．the composition of the topsoil is rather unstable

B．black carbon is washed away by heavy rains

C．organic matter is quickly lost due to heat and rain

D．long-term farming has exhausted the ingredients essential to plant growth

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1 Glaser made his discovery by （　　）．

A．studying patches of fertile soils in the central Amazon

B．examining pottery left over by ancient civilizations

C．test-burning patches of trees in the central Amazon

D．radiocarbon-dating ingredients contained in forest soils

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2 What does Glaser say about the regrowth of rainforests？

A．They take centuries to regrow after being burn

B．They cannot recover unless the vegetation is burnt completel

C．Their regrowth will be hampered by human habitatio

D．They can recover easily after slash-and-burn farmin

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3 From the passage it can be inferred that （　　）．

A．human activities will do grave damage to rainforests

B．Amazon rainforest soils used to be the richest in the world

C．farming is responsible for the destruction of the Amazon rainforests

D．there once existed an urban civilization in the Amazon rainforests

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