下图中画出了四种电场的电场线，各图中 M 、N 两点场强相同的是
答案：C
题目分析：电场线的疏密表示场强的大小，同一电场中电场线密集的地方场强大；电场线的切线方向表示电场的方向。两点场强相同是指两点场强大小相等方向相同。
A、A图中M 、N 两点场强大小相等，但方向不同；错误
B、B图中M 、N 两点场强方向相同，大小不等；错误
C、C图中M 、N 两点场强大小方向都相同，即两点场强相同正确；
D、D图中M 、N 两点场强大小方向都不同；错误
故选C
点评：容易题。电场线能形象地描绘电场中各点的场强的大小和方向，已知电场线的分布，能定性地获取电场的很多信息．此题要特别注意电场强度是矢量。
| A large part of effective leadership is dependent on something called "style". But style is difficult to teach, and what makes one leader great and another mediocre is not easily defined. Leadership always implies power, and a broad definition in this context is that leadership includes the power to influence thoughts and actions of others in such a way that they achieve higher satisfaction and/or performance. Over the past century, there have been three major approaches to understanding leadership. Identifying leadership traits, or the physical and psychological characteristics of leaders, was the first formal approach, and had a lot of intuitive appeal. It owed its origins to the mm of the century (about 1904) when trait studies began. At this time most American leaders came from certain wealthy families, the vast majority were white males, and there were some social norms about what leaders looked like (tall, square jaw, well groomed, etc.). The original assumption that "leaders are born, not made" has been discredited, because there were too many exceptions to the traits to give them any credibility. Beginning after World War II, in sharp contrast to the trait approach, the behavioral approach looked at what a leader does, what behaviors leaders use that set them apart from others. This approach assumed that leadership could be learned. Virtually all of the studies focused on classifying behaviors according to whether they fell into a process or "people approach" (satisfying individual needs), or a "task approach" (getting the job done). The basis for this classification was in the discovery in social psychology that every group needs someone to fulfill both these roles in the group for it to be effective. The earliest of these studies began in Ohio State University and the University of Michigan in the late 1940s. Many of the early trait and behavioral writers tried to make their ideas applicable to all leadership situations. The earliest situational approach to leadership was developed in 1958. This approach strived to identify characteristics of the situation that allowed one leader to be effective where another was not. The trend later developed toward the third approach, understanding the unique characteristics of a situation and what kind of leadership style best matches with these. |
The word "them" underlined in Paragraph 2 most probably means ______.
A．assumptions
B．leaders
C．exceptions
D．traits