3．We can learn from the passage that the scientists are working on ________.

　　A．the design of the new Web pages

　　B．the change of the food chain

　　C．the feeding of white sharks

　　D．the collection of DNA barcodes

　　解析：选D　细节理解题。第三段说明，收集海洋动物的条码是科学家的工作内容之一。

　　4．What may be the scientists' final goal?

　　A．To find new ocean species.

　　B．To learn the movements of white sharks.

　　C．To draw a picture of the distribution of white sharks.

　　D．To draw a global picture of the movements of animals.

　　解析：选D　推理判断题。根据最后一段可推知，这项研究会令科学家了解全球动物的分布并最终绘制出一幅海洋动物活动情况的全景图。

　　B

　　Windbreaks are barriers (屏障) formed by trees and other plants. Farmers plant these barriers around their fields, which help prevent the loss of soil and stop the wind from blowing soil away. They also keep the wind from damaging or destroying crops. Besides, extra trees and plants can be cut down and used or sold for wood.

　　Windbreaks can be highly valuable for protecting grain crops. For example, in parts of West Africa grain harvests were twenty percent higher in fields protected by windbreaks compared to fields without them.

　　But here is something interesting about windbreaks. They seem to work best when they allow some wind to pass through the barrier of trees or plants around a field. If not, then the movement of air close to the ground will lift the soil. Then the soil will be blown away. For this reason, a windbreak works best if it contains only 60 to 80 percent of the trees and plants that would be needed to make a solid line. An easy rule to remember is that windbreaks can protect areas up to 10 times the height of the tallest trees in the windbreak.

　　There should be at least two lines in each windbreak. One line should be large trees. The second line, right next to it, can be shorter trees or other plants with leaves. Locally grown trees and plants are considered the best choices for windbreaks. Trees reduce the damaging effects of wind and rain. Their roots help protect soil from being washed away. And trees can provide animals with shade from the sun.　

　　语篇解读：本文是说明文。介绍了防护林的有关知识。

　　5．The advantages of building a windbreak are as follows EXCEPT ________.

A．keeping the wind from destroying grain crops