GMAT逻辑无疑是verbal中最考验思维能力的题型，题目变化形式较多且缺乏规律性，这就需要练就灵活的逻辑思维和分析推理能力。而通过确定选项的范围相关性可以进行有效地排除，那如何来界定逻辑选项是否相关呢？下面我们就来看看具体的分析。
大家做逻辑题的时候都非常喜欢用“有关”“无关”来判断选项，无关选项其实就是因为跳出了探讨范围。但是很多时候大家做题也会选了一个跳出范围的选项，原因很简单：读题不仔细。我们下面通过两道题来看看，你读题的时候够不够仔细，是否真的抓对了探讨范围了呢？我们来看一个例子：
（原文）“Early in the twentieth century, Lake Konfa became very polluted. Recently fish populations have recovered as release of industrial pollutants has declined and the lake’s waters have become cleaner. Fears are now being voiced that the planned construction of an oil pipeline across the lake’s bottom might revive pollution and cause the fish population to decline again. However, a technology for preventing leaks is being installed. Therefore, provided this technology is effective, those fears are groundless. The argument depends on assuming which of the following?”
A. Apart from development related to the pipeline, there will be no new industrial development around the lake that will create renewed pollution in its waters.
C. The bottom of the lake does not contain toxic remnants of earlier pollution that will be stirred into the water by pipeline construction.
这里给出的两个选项都在保证不会有污染，那么哪个才是对的呢？这道题的题干大意是说人们担心湖底建油管会带来污染，但因为有一个有效的防泄漏科技，所以其实担心是多余的。其实，结论具体来说应该是“建油管不会带来污染”，这个就是我们找答案的时候划定的范围。C选项提到了“建油管”不会带来一些别的污染，这个可以确定是范围内的选项。再来看容易被错选的A选项，同样是说不会带来别的污染，但问题是，它说的是“除了建油管，其他事情不会带来污染”，可是我就是担心建油管会不会有污染呀，你都不谈建油管了我们之间还有什么好谈的那？这个就超出我们结论说的范围了。
但是，如果结论变成“湖不会被污染”，而不是“建油管不会带来污染”，也就是我们把结论的范围扩大了，那么C选项就变成了一个在范围内的选项，毕竟不论是建油管还是建大坝还是建什么，只要对湖水有污染，都在我们的探讨范围内了。
我们再来看一道类似的题：
（原文）“Many people suffer an allergic reaction to certain sulfites, including those that are commonly added to wine as preservatives. However, since there are several winemakers who add sulfites to none of the wines they produce, people who would like to drink wine but are allergic to sulfites can drink wines produced by these winemakers without risking an allergic reaction to sulfites. Which of the following is an assumption on which the argument depends?”
D. Apart from sulfites, there are no substances commonly present in wine that give rise to an allergic reaction.
E. Sulfites are not naturally present in the wines produced by these winemakers in amounts large enough to produce an allergic reaction in someone who drinks these wines.
同样地，两个选项都表示不会有过敏反应，那么哪个是对的？
题干大意是说酒的生产商不往酒里面添加亚硫酸盐，那么对亚硫酸盐过敏的人就可以放心地喝这些酒，而不用担心会产生亚硫酸盐过敏的情况了。
我们要注意，这里结论是“不会产生亚硫酸盐过敏的情况”，这个就是我们划定的找选项的范围。现在看选项，D选项说除了亚硫酸盐，酒里不含有其他致敏物质。大哥，我只讨论亚硫酸盐过敏的情况呀，其他物质会不会导致过敏我不关心的……很多看结论不仔细的同学就会选了这个选项，没有发现结论只针对亚硫酸盐过敏的情况进行讨论，擅自把其他致敏物质当成了他因来对待了。如果我们把结论换成“不会产生过敏反应”，也就是把范围扩大了，那么这个选项就是可取的了。
E选项说亚硫酸盐在酒里面不会自然产生，这个选项才是真正符合结论范围的，如果在酒里自然会产生，那么即使不额外添加，依然会产生对亚硫酸盐的过敏反应。
综合两道题来看，如果看题不仔细，你很可能会把结论当中一些表示范围的词给漏掉了，从而选了一个看似和结论有关其实跳出范围的选项。
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