题目内容
阅读理解
London—What could possibly be wrong with planting trees? The benefits(益处) are obvious: they firm the soil, soak up extra water and take carbon dioxide(二氧化碳) 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, which is generally believed to have done nothing favorable for man, blow out over the oceans from dry parts of North Africa and Central Asia. Tons of dusts are lifted and left as a thin film over the ocean surface. The dust fuels oceanic life.
Dust from China is carried east and left in the Pacific Ocean. If a tree-planting programme there is successful and the dust supply reduced, the next 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 yeas studying dust and says his work “shows clearly the complexity of the system and the importance of rat tinkering(修补) with it without understanding the results. For this reason the need to focus (集中) on cutting carbon dioxide giving off rather than monkeying(瞎摆弄) about with the land surface. ”
An American scientist, Robert Jackson, has shown that when native grassland areas are invaded 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．People usually hold the opinion that huge dust storms ________.
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A．cannot do anything favourable to human
B．can destroy the ocean life
C．can absorb carbon dioxide
D．can be controlled only by planting trees
2．Andy Ridgwell, the environmental scientist, believes that ________.
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A．dust plays a more important part than trees
B．trees shouldn't have been planted in dry places
C．environmental problems are more complex than realized
D．carbon dioxide is harmful to everything
3．Robert Jackson's experiment proves that ________.
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A．grassland areas should be coveted by forests
B．trees hold more carbon than grass
C．less carbon can make trees grow faster
D．carbon can make grass into dust
4．The underlined word “combat” in the text probably means ________.
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解析：
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1．A 导解：文中直接提到“我们一般认为对人类有害无益”． 2．C 导解：归纳判断题．从他的话“这一体系复杂，不能在没有了解其后果时到处修补，瞎摆布”．可知选C． 3．B 导解：从他的话中可知，研究表明种草改为种树后碳从土壤中流失了． 4．D 导解：从加粗部分来看，种树的出发点是为了与全球变暖做斗争，全球变暖是已经出现的情况，prevent不对． |
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