管网的起点水压是以哪一点的自由水头来确定的？

（一） Friends play an important part in our lives, and although we may take the friendship for granted, we often don’t clearly understand how we make friends. While we get on well with a number of people, we are usually friends with only a very few, for example, the average among students is about 6 per person. In all the eases of friendly relationships, two people like one another and enjoy being together, but beyond that, the degree of intimacy between them and the reasons for their shared interest vary enormously. As we get to know people we take into account things like age, race, economic condition, social position, and intelligence. Although these factors are not of prime importance, it is more difficult to get on with people when there is a marked difference in age and background. Some friendly relationships can be kept on argument and discussion, but it is usual for close friends to have similar ideas and beliefs, to have attitudes and interests in common--they often talk about ’ being on the same wavelength’. It generally takes time to reach this point. And the more intimately involved people become, the more they rely on one another. People want to do friends favors and hate to break a promise. Equally, friends have to learn to put up with annoying habits and to tolerate differences of opinion. In contrast with marriage, there are no friendship ceremonies to strengthen the association between two people. But the supporting and understanding of each other that results from shared experiences and emotions does seem to create a powerful bond, which can overcome differences in background, and break down barriers of age, class or race.

According to the author,______

A．all those who get on well with each other are friends

B．friends are closer than people who just get on well with each other

C．everyone understands clearly how to make friends

D．every student has 6 friends

作用在刚体同一平面上的三个互不平行的平衡力，它们的作用线汇交于（）。

半波整流电路的基本组成是由（）。

A.三极管和负载电阻

B.三极管和电容

C.二极管和三极管

D.二极管和电容、负载电阻

华夏银行进行尽职调查的范围包括新增问题贷款、涉及司法立案的授信业务和其他应展开尽职调查的授信业务。（）

肛瘘分为单纯性、（）、低位性、（）。