这个the poor poorer是什么意思

有这样一道题：

In some western countries，the rich are becoming richer，and __________.

A. the poor the poor                            B. poor poor      

C.the poor poorer                               D. poorer the poor

此题应选C。这是一个省略句，若补充完整应为：

In some western countries，the rich are becoming richer，and the poor are becoming poorer. 在有些西方国家，富人变得更富，而穷人则变得更穷。

前后两句谓语相同，后句承前省略。类似的有：

1. I am a teacher and my sister a nurse. 我是老师我姐姐是护士。

(...my sister a nurse=...my sister is a nurse)

2. John won the first race and Mick the second. 约翰赢了第一场比赛，米克赢了第二场比赛。

(...and Mick the second = ...and Mick won the second race)

3. In the accident the son was wounded，but the mother killed. 在事故中，儿子受伤，母亲丧命。(...but the mother killed=...but the mother was killed)

有时若后句的主语和宾语等与前句相同，则可一起省去：

4. He did it and quite successfully too at the beginning. 他这样做了，而且一开始就很成功。(=He did it and he did it quite successfully too at the beginning. )