Directions: Fill in each blank with a proper word given in the box. Each word can be used only once. Note that there is one word that you do not need.

A. countless        B. limits        C. comparison        D. essential        E. disappears        F. unique G. relatively        H. cleared        I. unfortunately        J. recycled

Rainforests, found in Earth’s temperate and tropical(热带的) zones, are some of the most biologically varied ecosystems on the planet. All rainforests share certain 【小题1】 features, including a closed canopy—the dense vegetation of the top branches that forms a roof above the forest floor, a damp and warm climate, and【小题2】 constant temperatures throughout the year. Most of the forest’s insect and animal life grows well in the canopy’s leafy and sunlit environment. The forest’s ground cover, by comparison, is small. Less than 2% of the sun’s light makes its way through the canopy and the darkness below. This darkness, along with the poor quality of the soils, 【小题3】 plant growth.

Rainforests are a(n)【小题4】 part of Earth’s total ecology. Huge amounts of water are absorbed into tree roots and【小题5】 into the atmosphere from the tree leaves through a process called transpiration(蒸腾作用). Tree roots also fix the soil in place and slow the run-off of rains into rivers and oceans. Through the process of photosynthesis(光合作用), rainforests absorb more carbon dioxide and give off more oxygen than any other ecosystem.

The rainforests are【小题6】 shrinking at a rapid rate as a result of the profitable ventures of farming, logging, and mining. When tropical rainforests are【小题7】 in order to raise cattle and crops, the nutrient-poor soils are quickly exhausted. When farmers move on to new areas, heavy rains and baking sun leave the land fruitless and lifeless. Logging and mining cause similar damage to the land and destroy the territory of【小题8】 millions of birds, insects and animals. By some estimates, an area of tropical rainforest the size of the state of Delaware【小题9】 in this way every month.