【托福阅读题型：Plant　Colonization修辞目的题】托福阅读中句子插入题是重要题型之一。根据托福阅读题型不同来进行专项练习，是短期提高托福阅读能力的有效方法。同学们需要多加练习哦!

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　　托福阅读修辞目的题：Plant　Colonization

　　【Paragraph 1】Colonization is one way in which plants can change the ecology of a site. Colonization is a　process with two components: invasion and survival. The rate at which a site is colonized by plants depends on　both the rate at which individual organisms (seeds, spores, immature or mature individuals) arrive at the site and　their success at becoming established and surviving. Success in colonization depends to a great extent on there　being a site available for colonization – a safe site where disturbance by fire or by cutting down of trees has either　removed competing species or reduced levels of competition and other negative interactions to a level at which　the invading species can become established. For a given rate of invasion, colonization of a moist, fertile site is　likely to be much more rapid than that of a dry, infertile site because of poor survival on the latter. A fertile,　plowed field is rapidly invaded by a large variety of weeds, whereas a neighboring construction site from which the　soil has been compacted or removed to expose a coarse, infertile parent material may remain virtually free of　vegetation for many months or even years despite receiving the sane input of seeds as the plowed field.(Plant　Colonization)

　　Why does the author mention a plowed field and a construction site in the passage?

　　○ To argue that sites that have been affected by human activity tend to be colonized slowly

　　○ To illustrate the kind of sites that may be invaded by weeds

　　○ To contrast sites in terms of their suitability for colonization

　　○ To explain that exposing or compacting the soil results in successful colonization

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