急!!还是比较的问题

According to public health officials, in 1998 Massachusetts became the first state in which more babies were born to women over the age of thirty than under it.

1. than
2. than born
3. than they were
4. than there had been
5. than had been born

答案A      NN能不能分析一下,than THOSE under it中的THOSE是不是省略了?应该不可以省吧?

这里的比较是两个年龄段的妇女的比较  如果加了those those可能指代baby 不好

后面如果补全的话，应该是than babies born to women under it，分析bcde没有一个符合省略条件的。

我觉得这里不是省略those的问题，因为those指代不清，到底是指babies还是women,所以不能用those.

比较的是WOMEN 不写出比较对象可以认为是UNDERSTOOD

比的应该是babies吧  than babies born to women under it

B如果改成 THAN THOSE BORN 可以吗

C的问题是不是THEY 不可以单独出现在后面的比较,而不是指代的问题呀

为什么不选B，有没有人给完整的解释？？谢谢了

用they的话就指代同一批babies了吧。

又要被30岁以上的妈妈们生一次又要被30岁以下的妈妈们生一次。