Many people seem to know well about the rain forests．Some people even go to the rain forests to spend some of their time trying to make friends with the plants and animals there．The scientists are actually hard at work studying the plants that grow in the very top level of a rain forest．Rain forests are one of the richest environments on Earth．They are home to millions of species of plants and animals．The red research raft provides scientists with a platform from which to study life in the treetops．Scientists can even sleep on the raft，so they can stay up in the treetops for days at a time．
    Rain forests cover only about 6 percent of Earth's land surface．However，they contain more than half of the plant species on Earth．Many of these plants provide useful medicines to use against human diseases．In fact，about 25 percent of prescription medicines in the United States are based on chemicals from rain forest plants．Scientists think that many new medicines might be developed from plants that are yet to be discovered．
    Unluckily，rain forests are disappearing．Rain forest trees are being cut down for wood．Huge chunks of the forests are cleared to provide land for farm animals and crops．Scientists haven't identified all the plants in these forests yet．Some scientists think thousands of kinds of plants that we'll never even know about are being destroyed each year．

根据短文内容，完成下列小题．
（1）Is it difficult for scientists to study the rain forest plants？

Yes．

Yes．

（2）Where probably is the red research raft？

In the treetops．

In the treetops．

（3）How much of Earth's land surface do rain forests cover？

About six percent．

About six percent．

（4）What do many of the rain forest plants mainly provide？

Useful medicines．

Useful medicines．

（5）Do you think that scientists will be able to know all about the rain forest plants？Why or why not？

No．Because thousands of kinds of plants are being destroyed each year．

No．Because thousands of kinds of plants are being destroyed each year．