prep 18,关于动词补出

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

答案是 D

我有一个疑问，这里的动词补出都用的是had,

因为前面不是完成时，而是是适宜动词，所以我觉得应该用did

不过既然答案是D，我就想问一下，动词的补出是可以补出原动词的吗？

例如

children eat more foods than their parents eat

children eat more foods than their parents do

哪句对呢？还是都可以？

当然可以补出实意动词。

两个例句都对！

这里的had是实意动词不是助动词，因为主句里有实意动词have对应had所以不会产生had是助动词的误解。

个人意见，仅供参考

好问题

不过,其他题目里被补出助动词的实意动词,好像基本上都是subject 能够"发出"的动作, 如:have ,be ,cost,  produce, destroy, employ etc (也包括sell). 不知道从这个角度讲, confront 和 这些动词是否有区别?