Here is an astonishing and significant fact：Mental work alone can’t make us tired.It sounds absurd.But a few years ago，scientists tried to find out how long the human brain could labor without reaching a stage of fatigue (疲劳)．To the amazement of these scientists，they discovered that blood passing through the brain，when it is active，shows no fatigue at all! If we took a drop of blood from a day laborer，we would find it full of fatigue toxins(毒素) and fatigue products.But if we took blood from the brain of an Albert Einstein，it would show no fatigue toxins at the end of the day.
So far as the brain is concerned，it can work as well and swiftly at the end of eight or even twelve hours of effort as at the beginning.The brain is totally tireless.So what makes us tired?
Some scientists declare that most of our fatigue es from our mental and emotional(情感的) attitudes.One of England’s most outstanding scientists，J.A.Hadfield，says，“The greater part of the fatigue from which we suffer is of mental origin.In fact，fatigue of purely physical origin is rare.”Dr.Brill，a famous American scientist，goes even further.He declares，“One hundred percent of the fatigue of a sitting worker in good health is due to emotional problems.”
What kinds of emotions make sitting workers tired? Joy? Satisfaction? No! A feeling of being bored，anger，anxiety，tenseness，worry，a feeling of not being appreciated－those are the emotions that tire sitting workers.Hard work by itself seldom causes fatigue.We get tired because our emotions produce nervousness in the body.
【小题1】What surprised the scientists a few years ago?A．Fatigue toxins could hardly be found in a laborer’s blood.B．Albert Einstein didn’t feel worn out after a day’s work.C．The brain could work for many hours without fatigue.D．A mental worker’s blood was filled with fatigue toxins.【小题2】According to the author，which of the following can make sitting workers tired?A．Challenging mental work.B．Unpleasant emotions.C．Endless tasks.D．Physical labor.【小题3】What’s the author’s attitude towards the scientists’ ideas?A．He agrees with them.B．He doubts them.C．He argues against them.D．He hesitates to accept them.【小题4】We can infer from the passage that in order to stay energetic，sitting workers need to .A．have some good foodB．enjoy their workC．exercise regularlyD．discover fatigue toxinsC
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(答案→)C
解析：本文为说明文，属于科普类文章。研究发现，单纯的脑力劳动并不会令人感觉疲劳，而真正令人感觉疲劳的是心理和情感态度，如烦躁、气愤、焦虑、紧张、担心、不被欣赏等。这些情感都是令脑力劳动者感觉疲劳的因素。
【小题1】解析：选C。细节理解题。根据第一段中“To the amazement of these scientists，they...no fatigue at all！”可知，令这些科学家们惊讶的是，大脑活跃时流经大脑的血液并没有表现出疲劳，故C项正确。A项与“If we took a drop of blood...and fatigue products.”意思表达相反，故排除；第一段最后一句指出在一天结束的时候，脑力劳动者的大脑血液中没有疲劳因素，这不是科学家们的惊讶之处，且与D项意思不一致，故排除B、D两项。
【小题2】解析：选B。细节理解题。根据倒数第二段最后一句可知，使脑力劳动者疲劳的主要原因是情感问题，最后一段指出了是哪些情感，故B项正确。
【小题3】解析：选A。推理判断题。本文主要介绍了科学家的研究成果，作者对此进行了进一步的分析、论证，对情感态度导致人疲劳的观点持肯定态度，并未对此进行质疑，故A项正确。
【小题4】解析：选B。推理判断题。根据最后两段的叙述可知，心理和情感态度是导致脑力劳动者疲劳的主要原因，因而保持好的心理状态才会感觉精力充沛；B项意为“喜欢他们的工作”，符合文意，这就避免了导致疲劳的烦躁、气愤等情感。其余几项都与导致疲劳的因素无关，故排除。