Question

There are several advantages in planting trees：they firm the soil，soak(渗透) up extra water and take carbon dioxide out of the atmosphere. However，it now turns out that planting trees could add to global warming. We all know that 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 the 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 and left as a thin film over the ocean surface.

Dust from China is carried east and left in the Pacific Ocean. If a tree­planting programme there is successful and the dust supply reduced, the net result may be that less carbon dioxide gets locked away in the ocean.

Andy，an environmental scientist has spent the past few years studying dust and says his work shows clearly the complexity of the system. For this reason the need is to focus on cutting carbon dioxide giving off rather than doing anything else.

Robert, an American scientist, 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 grass, so less carbon goes directly into the soil from trees.” said Robert.

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 fight against 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.

60．People usually hold the opinion that ________.

A. huge dust storms can destroy carbon dioxide

B. planting trees could reduce global warming

C. huge dust storms can destroy the oceans on the Earth

D. planting trees is the only way to control huge dust storms

61．Andy, an  environmental  scientist, believes  that________.

A. environmental problems are more complex than expected                 

B. trees shouldn't have been planted in dry places

C. dust plays a more important part than trees

D. carbon dioxide is harmful to everything

62．Robert's experiment proves that ________.

A. trees absorb more carbon than grass

B. carbon can turn grass into dust

C. less carbon can make trees grow faster

D. grassland areas should be covered by forests

63．The best title for this passage is “________”．

A. The importance of planting trees

B. The dust clouds soak up carbon dioxide

C. Is it really useful to plant trees to reduce global warming?

D. Why the soil carbon disappears

Answer 1

解析;推理判断题。从第一段的第二句“然而，现在证明植树可能会助长全球变暖”和最后一段第一句可推断出，人们通常所持的观点是“植树可能会减缓全球变暖”。

答案;B

解析;细节理解题。由第四段第一句中的“says his work shows clearly the complexity of the system”可知，这位环保专家认为环境问题比人们估计的要更复杂。

答案;A

解析;细节理解题。根据第五段内容可知，这位美国科学家通过研究发现，当树侵占了草坪的地方时，碳元素就从土壤中消失，分析其原因得知，与草相比，树在成长的过程中需要大量的碳，所以从树木那里直接进入到土壤里的碳就比从草里进入到土壤里的要少，即树比草吸收的碳要多。

答案;A

解析;主旨大意题。全文通过实例证明植树可能会助长全球变暖，所以C项最能突出主题，其他三项只是文章内容的一个部分或某部分中的一个事实。

答案;C