A B的区别在哪里呢！

斯巴达

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.

A.    than
B.    than born
C.    than they were
D.    than there had been
E.    than had been born

斯巴达

多谢！

ruimiss

就我的理解，这句话比较的是更多的孩子是由哪些超过三十岁的女人生的，比低于三十岁的女人。
这里的比较对象就是over the age of thirty和under  the age of thirty
it指代the age of thirty，几乎所有重复的都被省掉了。
而前面那句more babies were born to women因为在比较前后是完全重复的，因而也可以全部省略，B中莫名的省略了其他只留下了born反而易歧义，而且也应该是were born...