求助大全32

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

为什么E中最后不加do呢？究竟是主语并列还是主谓并列？疑惑。。。

ETS要求是简洁达意

此题目为主语的比较，一般要补出（情态）动词，是为了避免歧异

该句子：X will do less A and do B more adv. than Y  没有补出谓语，就表明不会引起歧义。参考版上有人说明是因为有两个动作比较，不会引起those 跟medication or weight比较的嫌疑。

此外，个人认为，主语比较补出（情态）动词，主要是在主谓宾齐全， 而且主语跟宾语的词性一样的时候。例如OG199:

X will ... devastate an area 100 times greater than will Y

如果不一样，例如一个是主语是名词，宾语或者表语是形容词（就这个意思，我不是太懂语法），也不容易引起混淆，就不用补什么了：

OG118.       X of A be more fragile than those(X) of B, 就无补be动词。

还有例如动词不极物，后面没有宾语，也无须补。