各位大虾，有关OG46的两个语法点不清楚，可否帮忙解释，谢谢！

46. 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.

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

1。为什么“require"及“gain"不用将来时，不是应该“X will happen if y happens(OG37)"

2。为什么”than"后不用补齐助动词"do"，但在OG12及OG19中都补齐了？

可否告之何种情况下需补齐助动词。

than后面何时补do的问题，我也一直想搞清楚。

期盼大虾献身说法！

1. ' A study showed ' So this has been proven, therefore it is a fact.

And for facts, we use present tense.

2. 'Do' should be placed after 'than those reaised in confinement' (do)

'Do' should be placed after 'than those reaised in confinement' (do)

If "do " can be ommitted ,why is the answer E of OG19 wrong?

"19. In addition to having more protein -than wheat does, the protein in rice is higher quality than that in wheat, with more of the amino acids essential to the human diet.

E rice has a protein higher in quality than

1,agree with loushang,because it is a proved fact rather than an imagined circumstances,so present tense here is ok.

2,the verb do should be deleted if the deletion does not cause any confusion.in the above mentioned circumstance, no confusion appears without do,so it is advisable to do so.

E rice has a protein higher in quality than

e is not correct because there is confusion when the verb is missing.the things in comparison change.the aimed comparison is between protein in rice and protein in wheat, but the consequence of omitting the verb is that protein is compared with wheat,distorting the original meaning.