The world's rainforests are an extremely valuable natural resource, to be sure, but not for their lumber or their land. They are the main cradle of life on Earth, and they hold millions of unique life forms that we have yet to discover. Destroying the rainforests is comparable to destroying an unknown planet-we have no idea what we're losing. If deforestation continues at its current rate, the world's tropical rainforests will be wiped out within 40 years.

　　1. Virtually all plant and animal species on Earth can be found in tropical rainforests.

　　2. There is not much change in the weather in the tropical rainforests all the year round.

　　3. The largest number of rainforests in the world are located on the African continent.

　　4. Below the canopy level of a tropical rainforest grows an overabundance of plants.

　　5. New tree seedlings will not survive to reach the canopy level unless ________.

　　6. Epiphytes, which form much of the under story of the rainforest, get all their water and nutrients from ________.

　　7. Stranglers are so called because they ________ by blocking the sunlight and competing for the nutrients.

　　8. Since rainforest bacteria and trees depend on each other for life, the relationship they form is termed ________.

　　9. Plant species are dispersed over a large area with the help of ________.

　　10. As we are still ignorant of millions of unique life forms in the rainforest, deforestation can be compared to the destruction of ________.

　　Unit 1

　　1. N 2. Y 3. NG 4. N

　　5. guaranteed 6. Internet access

　　7. two customer satisfaction programs / a customer hotline and a customer call-back program

　　8. higher prices of their pizzas

　　9. reckless driving by their drivers

　　10. the same