已知某正弦电压的最大值为311V，则其有效值等于（） A.220V B.210V C

Human relations have commanded people’s attention from early times. The ways of people have been recorded in innumerable myths, folktales, novels, poems, plays, and popular or philosophical essays. Although the full significance of a human relationship may not be directly evident, the complexity of feelings and actions that can be understood at a glance is surprisingly great. For this reason psychology holds a unique position among the sciences.

" Intuitive " knowledge may be remarkably penetrating and can significantly help us understand human behavior whereas in the physical sciences such common sense knowledge is relatively primitive. If we erased all knowledge of scientific physics from our world, not only would we not have cars and television sets, we might even find that the ordinary person was unable to cope with the fundamental mechanical problems of pulleys and levers. On the other hand, if we removed all knowledge of scientific psychology from our world, problems in interpersonal relations might easily be coped with and solved much as before. We would still " know " how to avoid doing something asked of us and how to get someone to agree with us: we would still " know " when someone was angry and when someone was pleased. One could even offer sensible explanations for the " whys " of much of the self’s behavior and feelings. In other words, the ordinary person has a great and profound understanding of the self and of other people which though unformulated or only vaguely conceived, enables one to interact with others in more or less adaptive ways. Kohler in referring to the lack of great discoveries in psychology as compared with physics, accounts for this by saying that " people were acquainted with practically all territories of mental life a long time before the founding of scientific psychology. "

Paradoxically, with all this natural, intuitive, commonsense capacity to grasp human relations, the science of human relations had been one of the last to develop. Different explanations of this paradox have been suggested. One is that science would destroy the vain and pleasing illusions people have about themselves; but we might ask why people have always loved to read pessimistic, debunking writings, from Ecclesiastes to Freud. It has also been proposed that just because we know so much about people intuitively, there has been less incentive for studying them scientifically: why should one develop a theory, carry out systematic observations, or make predictions about the obvious In any case, the field of human relations, with its vast literary documentation but meager scientific treatment, is in great contrast to the field of physics in which there are relatively few nonscientific books.

The author uses Ecclesiastes and Freud(Line 4, Para. 3)as examples in order to（）

A. find a satisfactory explanation to the human relations in their books

B. show the growing tendency to ignore scientific explanations of human relations

C. challenge the first analysis on the underdevelopment of the science of human relations

D. prove the unwillingness of people to abandon the pleasing fantasy in their mind

小明同学用一个焦距未知的凸透镜、蜡烛、光屏探究凸透镜成像规律．

①由图甲可知，凸透镜的焦距是_____cm．实验时，应使烛焰、凸透镜、光屏的中心大致在_____．

②如图乙所示，若在光屏上（光屏未画出）能得到清晰放大的烛焰实像，则蜡烛可能置于透镜左边a、b、c、d四点中的_____点上，从该点继续向左移动蜡烛，且保证凸透镜的位置不动，为是光屏上的像更清晰，应将光屏向_____ ．（填“左”或“右”）

③当蜡烛所成的像在凸透镜的2倍焦距以外时，则应将蜡烛放在蜡烛放在______．

一个正方体的六个面上分别写有1、2、3、4、5、6．把这个正方体任意上抛，落下后，数“1”朝上的可能性是______朝上是奇数的可能性是______．

肱骨髁上骨折并发正中神经损伤，会发生下列哪种畸形（）

A.杵状指

B.垂腕

C.猿手畸形

D.银叉畸形

E.枪刺刀畸形

所谓定轴轮系是指各齿轮的轴线相对机架都是（），而周转轮系是指至少一个齿轮的几何轴线相对机架不是固定的。