most unusual animals in the world. But many of these species may be in danger. Bushes and low­lying plants have started to take up too much space on the forest floor, providing fuel for wildfires. So scientists are considering using giant tortoises to help prevent the forest fires and thereby help the native wildlife in Madagascar.

　　Why? Long ago, giant tortoises lived all over Madagascar. They ate up many plants that grew on the forest floor. They also spread the seeds of native trees - keeping the ecosystem in check. But when humans settled on the island over 2,000 years ago, hunting caused the giant tortoises native to the island to become extinct.

　　Now, scientists plan to ship 300 close relatives of the extinct Madagascaran tortoises to the island. They hope that these tortoises will spread the seeds of native plants and chow_down_on the extra bushes - just like their relatives did long ago.

　　To find the relatives, scientists studied the fossils (化石) of Madagascar's extinct giant tortoises. They discovered that they were actually very similar to another group of giant tortoises that live on the Aldabra Atoll, a group of islands in the Indian Ocean. When the tortoises first arrive in Madagascar, they will live in an area closed off from the rest of the wildlife. There, researchers will watch the tortoises' every move to see how they will react to the native plants. If all goes well, the tortoises will be released into the wild.

　　Similar practice has been successful in other places. Take the island of Rodrigues, located east of Madagascar, for example. Seven years ago, tortoises were brought there. Now they are spreading seeds and keeping the bushes from taking over. If the same thing works in Madagascar, the giant tortoises may be used to help out other forests around the world.

　　语篇解读：非洲岛国马达加斯加为防止森林火灾和保持生态平衡，考虑引进一种巨型龟。

　　5．The underlined phrase "chow down on" is the closest in meaning to "________"．

　　A．walk around　　　　　　 B．eat up

　　C．go through D．live with

　　解析：选B　词义猜测题。根据画线部分后面的"just like their relatives did long ago"和第二段中的"They ate up many plants that grew on the forest floor."可知，"chow down on"在句中意为"吃掉"。

　　6．How will researchers deal with the tortoises to be introduced to Madagascar?

　　A．They will do an experiment with them.

　　B．They will always keep them off the wildlife.

　　C．They will make them adapt to native plants gradually.

　　D．They will compare them with the extinct tortoises in Madagascar.

解析：选A　细节理解题。根据第四段内容可知，在引进新的乌龟品种时，科学家们