[讨论]10th OG - 171/195，诚心请教

A recent report determined that although only 3% of drivers on Maryland highways equipped their vehicles with radar detectors, 33% of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.

The conclusion drawn above depends on which of the following assumptions?

The answer is: drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.

我想问的是，这个问题怎么思考，虽然看了OG的解释，我还是转不过弯来，请教大家解题思路方法。

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A proposed change to federal income tax laws would eliminate deductions from taxable income for donations a taxpayer has made to charitable and educational institutions. If this change were adopted, wealthy individuals would no longer be permitted such deductions. Therefore, many charitable and educational institutions would have to reduce services, and some would have to close their doors.

The argument above assumes which of the following?

The answer is: without the incentives offered by federal income tax laws, at least some wealthy individuals would not donate as much money to charitable and educational institutions as they otherwise would have.

但是题目中还有两个选项，我看也像答案，而且ETS的解释我不是很明白（黄底标出），请教有没有别的思路。

1. Money contributed by individuals who make their donations because of provisions in the federal tax laws provides the only source of funding for many charitable and educational institutions. 
ETS explained that as the argument need only assume that many institutions depend heavily, but not necessarily exclusively, on donations from such individuals.

2. Wealthy individuals why donate money to charitable and educational institutions are the only individuals who donate money to such institutions.
Explained by ETS that as far as the argument is concerned, there can be many other individuals who donate money to the institutions.

教你一个简单方法

assumption的实质是必要条件 转化成逻辑语言为： 只有。。。才

看到不能确定的答案就往里面代

我们来实践一下 ：所有的司机3%装了雷达 33%的因超速被罚款者装了雷达 结论 装雷达的司机更倾向于超速 （注意，因超速被罚款和倾向超速是两个概念 所以要得出结论 必须把这两个概念联系起来）

我们用只有 。。才。。来验证答案  只有“因超速而被罚款的司机比那些没被罚款的人更倾向于超速”才能得出结论“安装了雷达的司机更倾向于超速”  正确

同样地 只有“慈善机构基金的唯一来源是那些因为可以抵税而捐助人的捐献” 才能得出结论 “很多慈善机构不得不减少服务，甚至关门”  这显然错误，举个例子，90%来自于这些人 也同样能得出结论 所以只有后面的那句话不能成为必要条件

再下一条也是同理 你很容易举出反例 证明其不是必要条件

感谢楼上，貌似是一个深入浅出的方法，我实践看看