阅读理解。     LONDON: What could possibly be wrong with planting trees? The benefits

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阅读理解。     LONDON: What could possibly be wrong with planting trees? The benefits are obvious; they
firm the soil, take in extra water and take carbon dioxide out of the atmosphere. However, it now
turns out that planting trees could add to global warming.
     Tree roots do a great job of keeping soil firmly on the ground and out of the wind"s power. The
problem is that some of those dust clouds play an important part in soaking up carbon dioxide.
     Huge dust storms blow out over the oceans from dry parts of North Africa and central Asia.
Tons of dust are lifted as a thin film over the oceans surface. The dust fuels oceanic life.
     Dust from China is carried east and left in the Pacific Ocean. If a tree-planting program there is
successful and the dust supply reduced, the net result may be that less carbon dioxide gets locked
away in the ocean.
      Andy Ridgwell, an environmental scientist from the University of East Anglia, has spent the past
few years studying dust and says his work "shows clearly the complexity of the system and the
importance of not tinkering (粗劣地修补) with it without understanding the results. For this reason
the need is to focus on cutting carbon dioxide giving off rather than monkeying (瞎弄) about with the
land surface."
     An American scientist, Robert Jackson, has shown that when native grassland areas are invaded
(侵入) by trees, carbon is lost from the soil. "We are studying why the soil carbon disappears, but
one theory is that trees do a lot more of their growing above ground compared to grasses, so less
carbon goes directly into the soil from trees." says Jackson.
      In wet areas of the world, the gain from trees absorbing carbon dioxide above ground seems to
be outweighed by the loss of carbon from the soil below ground. Countries that plan to combat global
warming by planting trees may have to think again.
     Solutions to environmental problems are often more complex than they first appear, and
understanding the Earth"s climate is a very great challenge.1. According to this report, dust from storms can do the following except ________.A. harm the earth"s climate    
B. take in carbon dioxide  
C. feed the life in the ocean    
D. keep carbon dioxide locked in the ocean2. Andy Ridgwell believes that _____________.A. dust plays a more important part than trees
B. trees shouldn"t have been planted in the past
C. carbon dioxide is harmful to everything on the earth
D. environmental problems are far less simple than expected3. Robert Jackson"s experiment proves that ____________.A. grassland areas should be covered by forests
B. carbon can turn grass into dust
C. trees hold more carbon than grasses
D. less carbon can make trees grow faster4. The underlined word "combat" in the last but one paragraph means ________________.A. learn about      
B. live with        
C. fight against        
D. give up

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