请教：GWD4-Q19

Q19:

After several years of rapid growth, the healthy care company became one of the largest health care providers in the metropolitan area, while it then proved unable to handle the increase in business, falling months behind in its payment to doctors and hospitals.

A.   while it then proved unable to handle the increase in business, falling months behind in its payment to

B.    while it then proved unable to handle the increase in business and fell months behind in its payment to

C.   but then it proved unable to handle the increase in business, falling months behind in its paying

D.   but then proving unable to handle the increase in business, falling months behind in paying

E.    but then proved unable to handle the increase in business, falling months behind in paying

答案是E。请教为什么？谢谢！

使用while的话相比较C,D,E句子结构更加复杂.

payment to 的使用也不如paying + 名词来的好.