OG一个题，大神求问

小仙女rachel

A compelling optical illusion called the illusion of velocity and size makes objects appear to be moving more slowly the larger the objects are. Therefore, a motorist’s estimate of the time available for crossing a highway with a small car approaching is bound to be lower than it would be with a large truck approaching.
The conclusion above would be more properly drawn if it were made clear that the (assumption)
(A) truck’s speed is assumed to be lower than the car’s
(B) truck’s speed is assumed to be the same as the car’s
(C) truck’s speed is assumed to be higher than the car’s
(D) motorist’s estimate of time available is assumed to be more accurate with cars approaching than with trucks approaching
(E) motorist’s estimate of time available is assumed to be more accurate with trucks approaching than with cars approaching
请问这句话结论是什么意思

小仙女rachel

Fiona09 发表于 2017-9-8 17:10
引用一下版上某大神对这一题的解析，如下：

A compelling optical illusion called the illusion of veloc ...

感谢版主！！

Fiona09

引用一下版上某大神对这一题的解析，如下：

A compelling optical illusion called the illusion of velocity and size makes objects appear to be moving more slowly the larger the objects are. （这句是省略句，回过来是：A compelling optical illusion called the illusion of velocity and size makes objects appear to be moving more slowly, the larger the objects, the more slowly moving the objects are appeared to be.)Therefore, a motorist's estimate of the time available for crossing a highway with a small car approaching is bound to be lower  than that it would be with a large truck approaching.
题干：一种强制性的视觉误差叫做速度和大小产生的误差：越大的物体看上去越慢。

结论：因此当一个驾车人在估计能穿过高速的时间时，对开过来的小车的时间估计应该低于对大车的时间估计。（这就是说，其实大车的速度比人能看到感到的要快，但是由于人的视觉误差和物体大小有关，所以小车看上去会快，所以对小车估计的时间会比对大车估计的时间少。除非小车和大车是同一速度的，否则是无法比较时间的，因为我们无法比较他们的速度了）

A. truck's speed is assumed to be lower than the car's （同样的速度条件下，我们才能比较误差，如果不是同一个参数级别，不能得出结论）

B.truck's speed is assumed to be the same as the car's (在卡车和小车原来速度相同的情况下，我们才能比较视觉差的问题，如果他们速度本来就不一样，有快慢，题目的结论就无法成立，我们不知道小车原来就比卡车快，还是反之，这样自然影响判断他们的能穿过高速的时间）

C.truck's speed is assumed to be higher than the car's （理由同上）

D.mostoris's estimate of time available is assumed to be more accurate with cars approaching than with trucks approaching （本题说的是视觉对速度的判断误差和物体大小有关，视觉误差是一直存在的，不存在哪个更精确的问题。比如：你对物体的速度产生的视觉误差是固定的，不因为你看见一辆大车，你的视觉误差率大，而小车就误差率小）

E.motorist's estimate of time available is assumed to be more accurate with trucks approaching than with cars approaching （理由同上）

做这题的时候其实我没有思考那么细致，特别是题目的句子很凹口。但是题目的大概意思在读了一遍以后应该可以猜到的。类似于这样的比较必须有一个恒量，然后看两个变量的比较。如果没有一个参数是恒定的，那么结论是不可知。