1. The term “drug abuse" most often refers to the use of a drug with such frequency that it causes physical of mental harm to the user or impairs social functioning. Although the term seems to imply that users abuse the drugs they take, in fact, it is themselves or others they abuse by using drugs.
　　2. Pharmacologists, who study the effects of drugs, classify psychoactive drugs according to what they do to those who take them. Drugs that speed up signals passing through the nervous system, which is made up of the brain and spinal cord, and produce alertness and arousal and, in higher doses, excitabili­ty, and inhibit fatigue and sleep, are called stimulants. Drugs that retard, slow down, or depress signals passing through the central nervous system and produce relaxation, a lowering of anxiety, and, at higher doses, drowsiness and sleep, are called depressants. One distinct kind of depressants are those which dull the mind’s perception of pain and in medicine are used as painkillers, or analgesics. These drugs called narcotics.
　　3. It is not always easy to determine exactly when simple drug use becomes abuse. Thus it is far eas­ier to study who uses illegal psychoactive drugs than it is to study who abuses them. When researchers de­scribe patterns of drug abuse, then, they usually describe the more general phenomenon of drug use, whether it leads to abuse or not.
　　4. Drinking on the job is a social and economic problem with a long history. With the growing popu­larity of illegal drugs in the 1960s and 1970s, it was to be expected that their use in the workplace would emerge as a major issue by the 1980s. Estimates of employee drug use vary greatly, ranging from 10 per­cent to 25 percent for the proportion of workers who use drugs occasionally on the job. The safe perform­ance of some occupations-among them, airline pilot, air traffic.
　　5. From the 1920s until the 1960s, treatment of drug abuse in the United States was practically non­existent. During this period many officials did not believe that treatment was effective or necessary. Drug abusers and sellers were simply arrested and imprisoned, thereby discouraging use. The dramatic explo­sion in the use and abuse of a wide range of different drugs during the 1960s demonstrated the weakness of this theory. As a result, two treatment programs were developed during the 1960s.

　　词汇：frequency n.①屡次,频繁②频率③周率 analgesia n.痛觉丧失
　　psychoactive a.心理治疗的 alertness n.机警,机敏
　　alert ①a.警觉的;机警的②灵活的,活跃的 narcotic n.安眠药；麻醉剂
23. Paragraph 1________________.
24. Paragraph 3________________.
25. Paragraph 4________________.
26. Paragraph 5________________.
27. Drugs that speed up___________.
A. Patterns of drug abuse
B. Treatment
C. Drug testing in the workplace
D. Classification of psychoactive drugs
E. Definitio

28. Treatment of drug abuse in the United States was practically nonexistent from___________.
29. It is not always easy to___________.
30. Estimates of employee drug use very greatly, ranging from____________.
A. 10 percent to 25 percent for the proportion of workers who use drugs occasionally on the job
B. determine exactly when simple drug use becomes abuse
C. the 1920s until the 1960s
D. the 1960s until the 1970s
E. signals passing through the nervous system

参考答案
23. E 24. A 25. C 26. B 27. E 28. C 29. B 30. A