一道关于daylight visibility的逻辑题

为什么是E啊

文章讲的是，用这个law可以减少事故的发生率，特别是远离赤道的地区（因为那些地区白天的可见度较差）。而这个世界上唯一拥有这个法律的国家是远离赤道的，而不是美国。

这道题目的一开始也困扰了我很久，我一开始费解这道题的原因是无法区分远离赤道的国家跟美国的区别（因为美国也是赤道以北的）。这个是就是典型的被常识给误导了。这道题目定义美国跟远离赤道的国家是两个完全不同的地理位置，我们可以暂且认为美国是赤道上的或者是靠近赤道的国家。那么答案E：这个法律对交通事故的限制力对美国讲远远低于那个远离赤道的国家（有那个法律的国家）便言之有理。

In fact, the only countries that actually have such laws are farther from the equator than is the continental United States. 

 我理解的这句话是说 在远离赤道的国家中只有美国有这法律

还有下面这题为什么选C啊

The presence of microorganisms that produce a toxin causes seawater to turn brownish red， phenomenon known as a red tide. Sea otters do not feed in areas where clams， their main source of food， have become contaminated with this toxin. According to a proposed explanation of the otters' behavior， the otters sample the clams in a potential feeding areas and can taste any toxin in them.

Which of the following， if true， would most strongly indicate that the hypothesis described in the last sentence of the passage is not correct？

　　（A） In some of the areas where red tides occur， neither clams nor sea otters are indigenous species.

　　（B） The presence of sea otters in a given areas has a significant effect on which other marine organisms are to be found in that area.

　　（C） When seawater in an area unaffected by red tide is artificially dyed brownish red， sea otters do not feed on the clams in that area.

　　（D） If the clams in a given area are contaminated with toxins， sea otters move to other areas in search of food.

　　（E） Although very small amounts of the toxin produced during a red tide are not harmful， large doses can be fatal to animals the size of sea otters.