B

    Here is an astonishing and significant fact: Mental work alone can’t make us tired. It sounds absurd. But years ago, scientists tried to find out how long the human brain could labor without reaching a stage of fatigue (tiredness). 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 comes from our mental and emotional 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 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.

***第十八届中央委员会第五次全体会议，于2015年10月26日至29日在北京举行。全会听取和讨论了***受中央政治局委托作的工作报告。全会认为，到二〇二〇年全面建成小康社会，是我们党确定的“两个一百年”奋斗目标的第一个百年奋斗目标。全会强调，实现“十三五”时期发展目标，必须牢固树立并切实贯彻创新、协调、绿色、开放、共享的发展理念。这是关系我国发展全局的一场深刻变革。

请你依据所学知识回答下列问题：

把61.235精确到0.01是____；3.15万精确到____位．

按要求变换句子

这个妇女的亲人被洋人轧死了。

改为“把”字句

____。

已知m、n是两条不重合的直线，α、β是两个不重合的平面，下列命题中正确的是（  ）