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."
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 这道题答案是D 我想请问一下这个比较结构的后半部分补出一个had,我认为应该补出来的助动词是did,因为我认为前半部分中的have并不是完成时态的助动词,是动词表示“有”的意思,为什么后半部分补出来的是had而不是did呢?