[求助]PREP 18题

18. There is a widespread belief in the US and Western Europe that young people
have
                a smaller commitment to work and a career than their parents and
grandparents
                and that the source of the change lies in the collapse of the
'work ethic'.

A. a smaller commitment to work and a career than their parents and grandparents

B. less of a commitment to work and a career than their parents and grandparents

C. a smaller commitment to work and a career than their parents and grandparents

D. less of a commitment to work and a career than their parents and grandparents
had

E. a lessening of the commitment to work and a career than their parents and
grandparents had

A: 少助动词had会产生比较歧义，than前面有不止一个名词

B: 同上

C: 同上

D: correct

E: lessening of 应该改成less of，名词形式优于动名词；此外and a career和前面a lessening对称改变原意，the commitment to work和a career概念不对称

注意：比较结构助动词补充的原则，不会产生歧义

这道题目之前有过讨论，我的问题是D中的had是否正确，

我觉得如果had在这里作为助动词补出，那么应该补出的是did，因为题目没有任何迹象表明要用过去完成时。

如果had在这里作为实意动词，那么我就质疑是否可以在比较结构中补出实意动词。之前有网友说是可以，我就接受了。

但是今天看到白勇的语法书里说不可以的，所以我现在对这个had非常困惑，请nn指点。

下面是白勇的例题及解释：

P202/34.

The guiding principles of the tax plan released by the Treasury Department could have even a greater

significance for the economy than the particulars of the plan.

A.even a greater significance for the economy than

B.a significance that is even greater for the economy than

C.even greater significance for the economy than have

D.even greater significance for the economy than do     

E.a significance even greater for the economy than have

答案：D

排除ＣＥ的理由：根据省略原则1.比较从句中的have如果是实意动词就必须用do代替。如果have是助动词，根据省略原则

2.主句谓语动词短语使用“情态动词(could)+verb (have)”的形式，比较从句中应该保留could而不是have.

1）这里的had 我认为是作为实意动词。很明显their parents and grandparents 的动作发出在young people
发出动作之前。作为比较结构的补出实意动词是可以的。

OG里面有例子：OG92:

此题的正确答案就是补出了实意动词confronted .

2）白勇的语法很有价值，但是他的一些原则并不和GMAT完全一致。建议还是以OG的解释为最终原则。