求助：TT GWD 4-19

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.

1. while it then proved unable to handle the increase in business, falling months behind in its payment to
2. while it then proved unable to handle the increase in business and fell months behind in its payment to
3. but then it proved unable to handle the increase in business, falling months behind in its paying
4. but then proving unable to handle the increase in business, falling months behind in paying
5. but then proved unable to handle the increase in business, falling months behind in paying

答案是E,但我选A，谁能帮忙解释一下？

A中it指代??似乎劃線部份有代詞的大多有問題，且主詞是前面company，不用再重複用代詞指代。另外while好像是指時間觀念吧，表達對比應該用but，its payment不好，用動詞pay較好。個人的小見解，有錯誤請糾正。

concise is the priority in this question.

since there are conjuctions in each of the choices, it which refers to the subject is unnecessary.

Falling in paying is much more concise than falling in one's paying or payment.

In A, it is an ambigous pronoun which is unnecessary

好象没有payment to这个用法吧?有payment of and payment for

A B的payment to错