| 15. A researcher studying drug addicts found that, on average, they tend to manipulate other people a great deal more than nonaddicts do. The researcher concluded that people who frequently manipulate other people are likely to become addicts. Which of the following, if true, most seriously weakens the researcher's conclusion? (A) After becoming addicted to drugs, drug addicts learn to manipulate other people as a way of obtaining drugs. (B) When they are imprisoned, drug addicts often use their ability to manipulate other people to obtain better living conditions. (C) Some nonaddicts manipulate other people more than some addicts do. (D) People who are likely to become addicts exhibit unusual behavior patterns other than frequent manipulation of other people. (E) The addicts that the researcher studied were often unsuccessful in obtaining what they wanted when they manipulated other people.
答案是A, 我感觉D也是削弱. 而且比A好, 谁能指点一下? | 
