OG紫-67 关于optical illusion

羽依依

100. 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 that it would be with a large truck approaching.

the conclusin above would be more properly drawn if it were made clear that the:
A truck's speed is assumed to be lower that 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.mostoris'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

答案是B可以理解，但是C为什么错，OG解释是if the truck is moving faster than the car,the illusion must make the two vehicles appear to be moving at the same speed.解释本身就已经违背了题目中的信息了，而且如果truck的速度比car快，而a small car approaching is bound to be lower ，那么不是正好证明了illusion的存在么。

羽依依

嘿嘿 谢谢~大概能够理解的~有点钻牛角尖了~

miaoyin_tx

我之前和你一样选的C。认为这就像是个生物实验讲究的“同等变量”原则。看原题中，如果truck's speed is assumed to be higher than the car's，那么为什么a motorist's estimate 不估计小车和大车的时间会相同而是两者的大车的时间更短呢？你把B和C的assumption分别填到Therefore前面的两句之间去，就可以知道了。