[問題]GWD 23-23

[blackblood]

After several years of rapid growth, the healthy care company became one of the largest health care providers in the metropolitan area[u]while it then proved unable to handle the increase in business, falling months behind in its payment to [/u]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 (E)

請問這題(B)哪裡不好了
還有paying和payment有什麼差別呢
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[bonus]

請參考原發問討論貼
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http://www.formosamba.com/phpBB3/viewtopic.php?t=21267