听力原文：In order to diagnose and treat abnormal behavior, we have to start with clear def

听力原文： In order to diagnose and treat abnormal behavior, we have to start with clear definitions of what's meant by abnormal and normal. Criteria must be worked out for distinguishing one from the other in actual clinical cases. The word abnormal implies a deviation from some clearly defined norm. In the case of physical illness, the boundary lines between normality and pathology are often clearly delineated by medical science, making it easier to diagnose. On the psychological level, however, we have no ideal model to use as a base of comparison, nothing to help us distinguish mental health from mental disorder. The problem of defining abnormal behavior. via establishing just what is meant by normal behavior. has proved extremely difficult. However, as chapter 5 outlines, several criteria have been proposed. One norm described in detail in your text is personal adjustment. An individual who was able to deal with problems effectively without serious anxiety or unhappiness or more serious symptoms is said to be well adjusted. Personal adjustment as a norm has several serious limitations though. For example, it makes no reference to the individual's role in the group. How're we going to classify, for example, the a typical politician or businessperson who engages in unethical practices. Either might be a successful, happy, well-adjusted individual. Obviously, the welfare of the group, as well as that of the individual, must be considered, which brings me to the next approach.

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A．It is difficult to define

B．Its causes are often unknown

C．Psychologists disagree about how to treat

D．Its symptoms often go unnoticed