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

这句话后半句转折 but转折语气比while强烈 所以优选有but选项的 falling在这里表伴

随 以上可排除AB

but连接2个句子所以D错

paying这里表动作 实意动词优于其抽象名词形式 又因为but前后主语不变所以第二句it

可省略 －更简洁

所以选E