二、偷换概念(偷换中心词)
阅读当中错误选项还有一个特点，就是喜欢偷换概念。之前我们讲过偷换概念的一种形式，就是扩大表述范围。但这次讲的偷换概念，指的是偷换中心词。比如，原文中表述：小明喜欢吃草莓味的饼干。此时某个选项中就可能表述为：小明喜欢吃草莓味的糖果。虽然都是草莓味，但是中心词已经由饼干变成了糖果，这是完全不一样的。
举例：(2012年英语一text4)
Reform has been vigorously opposed, perhaps most egregiously in education, where charter schools, academies and merit pay all faced drawn-out battles. Even though there is plenty of evidence that the quality of the teachers is the most important variable, teachers’ unions have fought against getting rid of bad ones and promoting good ones.
As the cost to everyone else has become clearer, politicians have begun to clamp down. In Wisconsin the unions have rallied thousands of supporters against Scott Walker, the hardline Republican governor. But many within the public sector suffer under the current system, too.
39. The example of the unions in Wisconsin shows that unions
[A]often run against the current political system.
[B]can change people’s political attitudes.
[C]may be a barrier to public-sector reforms.
[D]are dominant in the government.
解析：该题由第一段第一句以及第二段第一句可知，正确答案为C。而错误选项中，A、B都为偷换概念。原文中二段首句中出现了politician政客，而A、B中分别出现了political system政治体系、political attitudes政治态度，三者都与政治有关，但是中心词却分别为人、体系、态度，截然不同。
