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
這題的答案是A但其他錯在哪呢
想請問這類型的題目該如何解啊
我總是錯這一類的
想請高手指教~感恩不盡!!!!!!!