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