20. A rise in the percentage of all 18-year-olds who were recruited by the armed services of a small republic between 1980 and 1986 correlates with a rise in the percentage of young people who dropped out of high school in that republic. Since 18-year-olds in the republic are generally either high school graduates or high school dropouts, the correlation leads to the conclusion that the republic’s recruitment rates for 18-year-olds depend substantially on recruitment rates for high school dropouts.
Which one of the following statements, if true, most weakens the argument?
A. A large number of 18-year-old high school graduates were recruited for the republic’s armed services in 1986 than in 1980. B. Many of the high-technology systems used by the republic’s armed services can be operated only by individuals who have completed a high school education. C. Between 1980 and 1986 the percentage of high school graduates among 18-year-olds recruited in the republic rose sharply. D. Personnel of the republic’s armed services are strongly encouraged to finish their high school education. E. The proportion of recruits who had completed at least two years of college education was greater in 1986 than in 1980.
参考答案：C 思路：题目的核心是要否定percentage of dropouts 与 percentage of recruitment的因果关系
A：典型的混淆相对数概念和绝对数概念，文中比较的是比率，选项给的是绝对数；
B：无关选项，和题目的核心比率没有太大关系。Tips: 注意many... only by.....这种表述。
C：正确，指出结论的错误属于false dilemma。
D：无关选项。此类错误属于false appeal。tips:注意.....（机构或人）strongly encourage something E：无关选项，percentage of those completed college education和题目的核心比率没有太大关系。
+++ 我的看法 本题有疑意. Conclusion: the republic’s recruitment rates for 18-year-olds depend substantially on recruitment rates for high school dropouts. Reason/ Evidence that supports: A rise in the percentage of all 18-year-olds who were recruited by the armed services of a small republic between 1980 and 1986 correlates with a rise in the percentage of young people who dropped out of high school in that republic. (18-year-olds in the republic are generally either high school graduates or high school dropouts) Question: weaken +++ | 
