[讨论]对答案有点小疑问(XDF蓝皮上一题)

A study commissioned by the Department of Agriculture showed that if calves exercise and associated with other calves, they will require less medication and gain weight quicker than do those raised in confinement.

A) associated with other calves, they will require less medication and gain weight quicker than do

B) associated with other calves, they require less medication and gain weight quicker than

C) associate with other calves, they required less medication and will gain weight quicker than do

D) associate with other calves, they have required less medication and will gain weight more quickly than do

E) associate with other calves, they require less medication and gain weight more quickly than

答案是E.  其它选项都可以排除,但总感觉E选项 than 后面应该加一个do. 为什么可以省略呢?

没人回答我~~~~ 

請問 可以給我這題在xdf藍書上的題號位置嗎？

我之前也在思考這題，但我現在忘了在那裡了。

这道是og11上的原题，紫色39，解释说这个比较是两种calves之间的，do扰乱了比较结构，必须去掉，不然是错的。

紫色106题也给出了一个补出的例子

Inuits of the Bering Sea were in isolation from contact with Europeans longer than Aleuts or Inuits of the North Pacific and northern Alaska

ans: isolated from contact with Europeans longer than were

这里补出were是因为原文有歧义，看不出因纽特人是和谁隔绝了，加上were，逻辑意思清楚