PREP2 中一道题

There is a widespread belief in the United States 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 that of 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 that their parents and grandparents had

为什么选D，不选C呢？是不是commitment不能用small来形容？那么D最后那个had如何解释？前面的have是时以动词，那么后面应该加did，从什么地方看出要用过去完成时呢?

我觉得在美语中have可能可以作为比较特殊的实意动词

这里是主语比较 young peole和parents..比较 但是young people后有宾语 所以补充谓语比较好 不会产生歧义

less是副词，修饰动词have。have a commitment是个动词词组，表示前后比较的句子里，修饰的话应选择副词修饰have，而非形容词smaller修饰commitment.否则会造成歧义。

比如两年raise costs的比较，也是用less而不是fewer.

还是不明白为什么不是did,而用had。XDF老师说，than后面的助动词，加优先于不加，但如果加错了(Had instead of did),还不如不加。Confused!!