對(duì)于準(zhǔn)備考托福的同學(xué)們來(lái)說(shuō)，不知道準(zhǔn)備得怎么樣呢？今天就和出國(guó)留學(xué)網(wǎng)的小編一起來(lái)看看TPO閱讀TPO1-3 Timberline如何用于托福寫(xiě)作？
素材原文
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.
目前還沒(méi)有一個(gè)普遍認(rèn)同的解釋來(lái)說(shuō)明為什么會(huì)在樹(shù)帶界線上出現(xiàn)樹(shù)木停止生長(zhǎng)這種戲劇化的現(xiàn)象。多種環(huán)境因素都起到作用，例如，積雪過(guò)多會(huì)讓樹(shù)木透不過(guò)氣，雪崩和雪移能摧毀樹(shù)木；長(zhǎng)時(shí)間積雪縮短了有效生長(zhǎng)季節(jié)的時(shí)間，樹(shù)苗無(wú)法生長(zhǎng)；另外，風(fēng)速會(huì)隨著海拔的升高而增加，增加樹(shù)木承受的壓力，很明顯，正是這種風(fēng)速帶來(lái)的壓力導(dǎo)致樹(shù)木在高緯度地區(qū)發(fā)生變形。一些科學(xué)家提出，隨著海拔的上升而不斷增強(qiáng)的紫外線、野生山羊等動(dòng)物的放養(yǎng)，都是導(dǎo)致樹(shù)帶界線形成的因素?；蛟S最重要的環(huán)境因素是溫度，因?yàn)槿绻L(zhǎng)季節(jié)太短并且氣溫太低，樹(shù)芽和樹(shù)苗都無(wú)法充分地成長(zhǎng)而存活過(guò)冬季。
素材結(jié)構(gòu)
There is still no universally agreed-on explanation for why 給出問(wèn)題. Various factors may play a role. 第1個(gè)因素， for example， can 第1個(gè)因素的解釋. Some have proposed that 第2個(gè)因素 may play a role， while 第三個(gè)因素 may be another contributing factor. Probably the most important factor is 第4個(gè)因素， for 第4個(gè)因素的解釋.
素材示范
目前還沒(méi)有一個(gè)普遍認(rèn)同的解釋來(lái)說(shuō)明為什么那么多來(lái)自世界不同地方的、那么多人、那么看重工資在找工作的時(shí)候。多種因素都起到作用。例如，虛榮心會(huì)促使找工作的人更喜歡高工資的職位。一些人提出，一個(gè)好的工作環(huán)境會(huì)起到作用。工作的成就感或許是另一個(gè)因素。或許最重要的是生活壓力，因?yàn)橐粋€(gè)體面地生活僅僅是一個(gè)夢(mèng)幻如果沒(méi)有充足的收入。