精选优质文档-倾情为你奉上2012A根据短文内容，从短文后的选项中选出适当的选项补全短文。(共5小题，每小题l分；计5分) The earth is about 4,600 million years old. We humans have lived on the earth for only 35,000 years, but during this period we have changed our planet a lot in many ways. 1 All over the world, people have cut down millions of trees, so more and more kinds of animals and plants are disappearing. In big cities, cars and buses have polluted the air. Factories have also polluted the land and the water.
