OG verbal分册 38题，助动词补出算错？？？

peby1223

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 confi nement.
(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
正解是E，关于动词的时态平行，以及quickly副词修饰我没有问题。
但是OG在解释原句中说 the verb do ungrammatically interrupts the comparison and should be eliminated，即 最后一句的比较结构被do打断
请问：
这个do不是算一个助动词补出么，居然算语法错误？

如果正解E选项这么说
They associate with other calves, they require less medication and gain weight more quickly than X.
X1=do those raised in confi nement
X2= those raised in confi nement do
那么X1和X2哪个正确？

xiqiong

BY RON： 有DO其实也是对的
that would also be correct; the split between "...than..." and "...than do...", in this problem, is just meant to be an annoying distraction -- both versions are ok.

you would *need* the "do" if either of the following were true:
1) the verb in the other half of the comparison were written in a different tense;
2) the sentence would be ambiguous without it.

since neither of these is true, both versions are fine.

但是，GAMT比较需要补出助动词的情况在于有歧义，或是，时态发生了变化。
我们平时说的 A do sth. than B do. 是为了避免 B和 宾语发生歧义。 但是，你看看，这句话是不是带了两个并列的宾语？ 这样其实就没有歧义的可能性。 所以不需要DO的。

suzibi

因为前面有两个动词require&gain,如果助动词do补出的话，到底是指代谁？说不清，所以补出错

enkyklios

我觉得Do用上以后会指代不清，这应该不是没有必要用，而是用了会错。