第3部分：概括大意与完成句子(第23～30题，每题1分，共8分)

　　下面的短文后有2项测试任务：(1)第23～26题要求从所给的6个选项中为第2～5段每段选择1个最佳标题;(2)第27～30题要求从所给的6个选项中为每个句子确定1个最佳选项。

　　ecosystem

　　1 the word "ecosystem" is short for ecological (生态的) system. an ecosystem is where living creatures expand within a given area. you can say that an ecosystem is the natural environment where biological organisms (生物) such as plants, animals and humans co-exist in this world. so naturally that includes you and me. yes, we are all members of an ecosystem!

　　2 there are different kinds of ecosystems depending on the type of surface or environment. most are naturally made such as the ocean or lake and the desert or rainforest. some are man-made or artificial to encourage co-habitation (兴居) between living and non-living things in a monitored environment, such as a zoo or garden.

　　3 plants make up the biggest group of biological creatures within an ecosystem, and that's because they are the natural food producers for everyone. plants raised in the earth need air and collect sunlight to help them grow. when they grow, the plants and its fruits or flowers eventually become a source of food to animals, microorganisms (微生物) and even humans, of course. food is then converted to energy for the rest of us to function, and this happens in a never-ending cycle until the living creatures die and break up back in the earth.

　　4 ecosystems are the basis of survival for all living things. we depend on plants and animals for food. in order for us to exist, we need to grow and care about other organisms. we also need to care for the non-living things within our environment like our air and water so we can continue living as a population. since plants, animals and humans are all of various species (物种), we all play a role in maintaining the ecosystem.

　　5 to preserve our ecosystems, we should stop using too much energy, which happens when we consume more than our share of resources. humans should not disturb the natural habitat (栖息地) of plants and animals, and allow them to grow healthily for the cycle to continue. too many people in a habitat can mean displacement (搬迁): imagine being thrown out of your home because there is no more space for everyone. worse, overpopulation can also ruin the environment and cause destruction of existing plants and animals.

　　23. paragraph 2 _________

　　24. paragraph 3 _________

　　25. paragraph 4 _________

　　26. paragraph 5 _________

　　a. what can we do to help protect ecosystems?

　　b. what are different types of ecosystems?

　　c. what is an ecosystem?

　　d. what destroys ecosystems?

　　e. how does an ecosystem work?

　　f. why are ecosystems important?

　　27. in an ecosystem, plants, animals and humans live together in _________.

　　28. plants are essential in an ecosystem because to other living creatures they are _________.

　　29. plants, animals and humans are all effective in _________.

　　30. to protect our ecosystems we should not use more than _________.

　　a. our share of resources

　　b. a biological creature

　　c. a given area

　　d. the maintenance of the ecosystem

　　e. the source of food

　　f. various species