托福阅读修辞目的题是阅读考试中比较常见的一种题型，tpo则是托福阅读备考最权威的材料 ，所以托福小编综合二者，为大家集中整理了tpo阅读中考察的修辞目的题及其对应的解析，供大家参考使用。本文带来的是tpo1-1的修辞目的题，一起来看看吧。
TPO1-1 Timberline Vegetation on Mountains
paragraph 4
There is still no universally agreed-on explanation for why there should be such a dramatic cessation of tree growth at the upper timberline. Various environmental factors may play a role. Too much snow, for example, can smother trees, and avalanches and snow creep can damage or destroy them. Late-lying snow reduces the effective growing season to the point where seedlings cannot establish themselves. Wind velocity also increases with altitude and may cause serious stress for trees, as is made evident by the deformed shapes at high altitudes. Some scientists have proposed that the presence of increasing levels of ultraviolet light with elevation may play a role, while browsing and grazing animals like the ibex may be another contributing factor. Probably the most important environmental factor is temperature, for if the growing season is too short and temperatures are too low, tree shoots and buds cannot mature sufficiently to survive the winter months.
10. In paragraph 4, what is the author’s main purpose in the discussion of the dramatic cessation of tree growth at the upper timberline?
○To argue that none of several environment factors that are believed to contribute to that phenomenon do in fact play a role in causing it.
○To argue in support of one particular explanation of that phenomenon against several competing explanations.
○To explain why the primary environmental factor responsible for that phenomenon has not yet been identified.
○To present several environmental factors that may contribute to a satisfactory explanation of that phenomenon.
解析 以dramatic cessation of tree growth at the timberline为关键词定位至本段第一句，说对于这个cessation没有统一的解释，接着后面就说了有好多种解释，作者没说他认为哪个对，也没解释为什么没有一致意见，所以答案是D，提供了多种解释，A说所有都不对，B说支持其中一个，C说解释为什么没有一致意见都错了
[4]目前还没有一个普遍认同的解释来说明为什么会在树带界线上出现树木停止生长这种戏剧化的现象。多种环境因素都起到作用，例如，积雪过多会让树木透不过气，雪崩和雪移能摧毁树木;长时间积雪缩短了有效生长季节的时间，树苗无法生长;另外，风速会随着海拔的升高而增加，增加树木承受的压力，很明显，正是这种风速带来的压力导致树木在高纬度地区发生变形。一些科学家提出，随着海拔的上升而不断增强的紫外线、野生山羊等动物的放养，都是导致树带界线形成的因素。或许最重要的环境因素是温度，因为如果生长季节太短并且气温太低，树芽和树苗都无法充分地成长而存活过冬季。
以上就是托福阅读tpo1-1中的修辞目的题及其解析，大家可以在备考的时候参考复习，希望能够帮助大家的考前准备。最后前程百利祝大家都能取得理想的托福考试成绩。
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