American scientist say that they believe trees can warn each other of danger releasing chemicals into the air.__1__ The theory was announced by the National Science__2__ Foundation is the result of studies carried out by scientist in the states of Washington and New Hampshire. The scientists said they found that when trees are against attack by disease or insects, nearby__3__ trees take the same offensive actions as the trees__4__ being attacked. And they said it appears that the trees being attacked may produce and send out chemicals to warn the other trees. A United Nations‘report says Asian countries are faced major environ-__5__ mental problems. The report released in Bangkok said that parts of China, India, Iran, Afghanistan and　Pakistan were threatened by man-made and natural__6__ events that turn productive land into deserts. I said the most serious threat against the area is the rapid expansion of Asia's rain forests, or woods, especially__7__ in Malaysia, the Philippine and Thailand. The report said the reduction in woods areas have already led to __8__ increased flooding, water shortages in the dry seasons and the loss of farm lands. A top UN official said that as much as 70% of the woods in Asia would be gone in__9__ 20 years unless actions are taken now to save it.__10__

　　答案 在releasing前加by。用by引导releasing chemical into the air，作方式状语 删除was或在was之前加which/that。或过去分词announced或用which/that was announced 做定语修饰the theory。The theory的谓语动词为isagainst—under。习语（be）under attack，受攻击 offensive—defensive。根据常识，当生物收到外界的威胁时，也会进行自卫 faced—facing或在faced之后加with。动词face作“面临、应对”解时，有两种结构：被动态“主语+be+faced with+宾语”，主动态“主语+face+宾语”

　　6. were—are。报告的发布是在过去的考试吧某个时候，所以主语中的谓语动词发生在过去时，但报告的内容陈述的是一个事实，谓语动词应该是一般现在时

　　7. expansion—shrinking。与上文“可耕地变成沙漠”一样，亚洲的雨林面临快速减缩，而不可能扩大，而且下文中有the reduction in woods areas

　　8. have—has。主语为the reduction in woods areas

　　9. would—will。UN官员陈述的是一个完全可预见的事实

　　10. it—them。them指代the woods