10．Does stress cause gray hair？Many people believe that tension and stress can cause your hair to lose its color．In fact，it is an old wives tale that being upset all the time can result in premature（過早的） graying．Here is a closer look at this situation and why some believe that this old wives tale could be true．
As one ages，the hairs on the head also age．In fact，just about everything on the human body begins to show signs of wear and tear after a while．The joints wear and become stiff and skin wears and becomes wrinkled．Hairs on the head grow and eventually die．They are replaced，but in the process something else happens．
When new hairs are replaced，the color or pigment（色素）is also added to them．However，as one ages，this pigment becomes less and less available．At first，hairs will have a limited amount of pigment and they will appear to be grayish in color．In time，they will lose all of their pigment and will be white．Many things are known to cause graying．a(chǎn)nd genetics（遺傳學(xué)） is a very powerful factor．If one of your parents turns gray at an early age，there is a good chance that you will too．Some people begin the graying process in high school，while others may be over the age of forty．
Constant worry and tension can have many harmful effects on the human body．It is a known fact that stressful times can cause one to suffer hair loss．It would make sense that if it can cause these problems，perhaps it also may contribute to graying．However，there is no sound evidence to support this．
On the other hand，many medical professionals believe that there may be a link：between graying and a constant state of anxiety or tension．Does stress cause gray hair？There is no scientific evidence to support the theory，but it is best to avoid stressful situations．
25．The underlined phrase in the first paragraph most probably meansA．
A．silly remarks
B．clever remarks
C．exciting remarks
D．disappointed remarks
26．The second paragraph mainly tells usB．
A．every part of body is replaced with age
B．every part of body ages with age
C．skin becomes wrinkled with age
D．hairs will grow weak but not die
27．From the passage we can infer thatC．
A．stressful situations can be of benefit．
B．gray hair has nothing to do with tension．
C．stress causing gray hair is still in question
D．sound evidence has been found．
28．What might play the most important role in the graying process？B
A．Genetics and the amount of sleeping time
B．The amount of pigment and genetics
C．The amount of food people eat and living environment
D．Genetics and the amount of water people drink．
分析 本文是一篇說明文，介紹了白發(fā)產(chǎn)生的原因和與人的壓力、緊張情緒的關(guān)系．雖然科學(xué)上的依據(jù)還處于探索階段，但是為了我們的健康，最好還是避免緊張壓抑的消極情緒．
解答 25．A．考察對短語的理解，根據(jù)下文"Here is a closer look at this situation and why some believe that this old wives tale could be true．"，讓我們來深入了解一下這種狀況和為什么有的人會相信這種說法．可推理出這種說法是不正確的．而且通過全文也可知道這種說法并沒有科學(xué)依據(jù)．因此應(yīng)當(dāng)是愚蠢的說法．故選A．
26．B．內(nèi)容歸納題．注意到第二句的"everything on the human body"就可選出答案，隨著年齡的增長，頭發(fā)也會老化，事實上，身體的每一個部分都有老化的跡象．故選B．
27．C．細節(jié)理解題．最后一段"There is no scientific evidence to support the theory"，說明壓力會導(dǎo)致頭發(fā)變白依舊是一個未解決的問題，故選C．
28．B．細節(jié)理解題．第三段首句即提到新頭發(fā)產(chǎn)生時就有色素pigment，隨著時間過去，色素會減少．而后半段"and genetics is a very powerful factor"則說明了基因?qū)︻^發(fā)變白的重要性．故選B．
點評 本文是一個科教類閱讀理解，題目涉及多道細節(jié)理解題，做題時結(jié)合原文和題目有針對性的找出相關(guān)語句進行仔細分析，結(jié)合選項選出正確答案．推理判斷題也是要在抓住關(guān)鍵句子的基礎(chǔ)上合理的分析才能得出正確答案，切忌胡亂猜測，一定要做到有理有據(jù)．
