Test1-82.

Each year companies in the United States could save as much as $58 billion annually by preventing illness among employees and gain as much as $200 billion through improving performance of workers if they simply provided offices with cleaner air.

(A) annually by preventing illness among employees and gain as much as $200 billion through improving performance of workers if they simply provided
(B) annually if they prevented employee illness and gain as much as $200 billion through worker performance improved by simply providing
(C) annually in employee illness prevention and gain as much as $200 billion through worker performance improved by simply providing
(D) in employee illness prevention and gain as much as $200 billion through improving performance of workers if they simply provided
(E) by preventing illness among employees and gain as much as $200 billion through improved worker performance if they simply provided

Ans:(E)

(A)(B)(C)redundant
each year + annually

Why not (D)?
I think (D) is parallel. Thx