大家来看看这道题,答案有没有问题?

Because her second exam had fewer mistakes on it than the first, the student was allowed to progress to the next level of class, even though it was clear she had not yet fully mastered all the aspects of the subject.

A) .....
B) Because her second exam had fewer mistakes on it than did her first

答案选A.

我选B.比较句than后面的句子助动词或情态动词不是应该补出来吗?

IF "on it" is removed, the following expression is correct.

Because her second exam had fewer mistakes than did her first,

IF "on it" is kept, "the first" is parallel to "it". ie. "on"  modifies  both "it" and "the first".

Because her second exam had fewer mistakes on it than the first, =

Because her second exam had fewer mistakes on it than on the first exam,

同意楼上的分析，不过这样的话，答案应该选B.

答案是A呀，这道题补全了应该是这样：

Because her second exam had fewer mistakes on it than （had) the first (exam).。

这里的had是实义动词，B中补出助动词did补错了。还有这个her first总感觉应该补全成her first exam。the first比较清楚。

B里面had就是did have, 补出did没有错。

A里面，如4楼分析，the first有与it平行之嫌，补全的话是: Because her second exam had fewer mistakes on it than her second exam did on the first exam.

这一点我有不同看法，关于ETS里面所出的比较考题，绝大部分都是比较的是主语。这题也一样。4楼的解释非常牵强。这里B中的助动词补出有问题。即使是did have的话也不可能只补出did。逻辑意思不清。

另外XDF的老师也讲过一句：关于这个谓语动词补出还是不补出，关键是看补出的对不对，补对了则为正确答案，补错了则没有补出的为正确答案。

不过CD里前辈总结的是补出不补出要依据逻辑意思是否清晰决定，遵循简洁的原则。在不补出而逻辑意思清楚的情况下，不补出为正确答案。（这一点个人认为在实战中很难判断）。而新东方老师所讲的可以从ETS的题中得到证实。

OG224比较的就是主语，不过选项里补出了were, 所以才明确表示比较的是主语。因为在两者之间多了个europeans, 会造成比较的不平行。我觉得4楼的分析很符合ETS的思路。

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

(A) in isolation from contact with Europeans longer than

(B) isolated from contact with Europeans longer than

(C) in isolation from contact with Europeans longer than were

(D) isolated from contact with Europeans longer than were（D）

(E) in isolation and without contacts with Europeans longer than

补出的是助动词，而不是整个实义动词。OG224补出的是were助动词，而不是整个动词were isolated. 所以，我觉得这里补出did没有错。比如下例，补出的是did, 而不是encountered.

In the United States, trade unions encountered far more intense opposition against their struggle for social legitimacy than the organized labor movements of most other democratic nations.

(A) against their struggle for social legitimacy than

(B) in their struggle for social legitimacy than did

(C) against their struggle for social legitimacy as

(D) in their struggle for social legitimacy as did（B）

(E) when they struggled for social legitimacy than has

首先更正我之前的讨论：

这里举出大全491：

1.        Local residents claim that San Antonio, Texas, has more good Mexican American restaurants than any city does in the United States.

(A) any city does

(B) does any other city

(C) other cities do

(D) any city（B）

(E) other cities

这道题我仍然觉得答案是A；理由如下：

首先分析A和B：将其补全如下：

A：Because her second exam had fewer mistakes on it（second exam） than the first （exam）

B：Because her second exam had fewer mistakes on it （second exam） than did （had） her first (exam)

大家有没有注意到B中的on it；很明显B中比较的是主语，此时这个on it则显得完全多余，去掉on it句意更清晰。

A中正如4楼所说比较的是it（second exam） than the first （exam），这里的on it 就显的很合理。我想这里就是ETS的狡猾之处吧。应该是比较反常的一道比较题。个人意见，希望继续讨论！