作者在短文中多次使用need和important等詞匯，還使用了一系列同義詞或相關(guān)詞、反義詞或?qū)?yīng)詞等，如：
(1)teachers—adults;
(2)young adults—typical teenage lifestyle—teenagers—young teens—students;
(3)emotional, intellectual and physical changes—growing bodies—new bodies—new intellectual and emotional challenges;
(4)achieving success—accomplishment—winners—successful;
(5)plan activities—a variety of small clubs—some kind of organization—organization—a variety of activities—organized;
(6)winners—losers 等。
借助這些相關(guān)詞組成的語(yǔ)意鏈我們可以更好地把握主題：教師應(yīng)針對(duì)青少年的特點(diǎn)組織活動(dòng)以幫助學(xué)生們成長(zhǎng)。
請(qǐng)注意2005年的短文中黑體字和斜體字的提示：
The human nose is an underrated tool. Humans are often thought to be insensitive smellers compared with animals, but this is largely because, unlike animals, we stand upright. This means that our noses are limited to perceiving those smells which float through the air, missing the majority of smells which stick to surfaces. In fact, though, we are extremely sensitive to smells, even if we do not generally realize it. Our noses are capable of detecting human smells even when these are diluted to far below one part in one million.
Strangely, some people find that they can smell one type of flower but not another, whereas others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate particular smell receptors in the nose. These receptors are the cells which sense smells and send messages to the brain. However, it has been found that even people insensitive to a certain smell at first can suddenly become sensitive to it when exposed to it often enough.
The explanation for insensitivity to smell seems to be that the brain finds it inefficient to keep all smell receptors working all the time but can create new receptors if necessary. This may also explain why we are not usually sensitive to our own smells—we simply do not need to be. We are not aware of the usual smell of our own house, but we notice new smells when we visit someone else's. The brain finds it best to keep smell receptors available for unfamiliar and emergency signals such as the smell of smoke, which might indicate the danger of fire.
本文分析了人們?yōu)槭裁吹凸廊祟?lèi)鼻子作為嗅覺(jué)工具的靈敏性，共分三個(gè)自然段，除反復(fù)出現(xiàn)與“低估人類(lèi)嗅覺(jué)”和“人類(lèi)實(shí)際嗅覺(jué)能力”有關(guān)的文字外，每段都有表示原因的句型。第一段斜體字 are often thought to be insensitive smellers和 do not generally realize it等指出人們“人類(lèi)的嗅覺(jué)不如動(dòng)物靈敏”的認(rèn)識(shí)誤區(qū)。緊接段首句的but this is largely because句型提出產(chǎn)生錯(cuò)誤看法的原因：“人類(lèi)直立行走；”并以表示轉(zhuǎn)折和強(qiáng)調(diào)的連接詞引入與人們常識(shí)不符的事實(shí)：“然而，事實(shí)上我們的嗅覺(jué)是極為靈敏的，即使人們一般都沒(méi)有意識(shí)到這一點(diǎn)。”第二段同樣分析為什么有些人似乎對(duì)某些氣味不夠靈敏，做出解釋之后同樣用事實(shí)說(shuō)明不應(yīng)低估他們的嗅覺(jué)能力，這些人的嗅覺(jué)會(huì)“突然變得敏感起來(lái)”。第三段以The explanation for insensitivity to smell seems to be that…和This may also explain why…等句子進(jìn)一步解釋人類(lèi)對(duì)氣味似乎不敏感的原因：“為提高工作效率，人腦不需要讓所有嗅覺(jué)細(xì)胞同時(shí)工作�！蓖瑯釉谔岢隼碚撝蠼o出生活中的例子。
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