With so much public scrutiny of politicians' private lives, many aspiring lawmakers are dissuaded from seeking office because the exposing of their past indiscretions to the public would prove embarrassing
A.
B. of past indiscretions exposed to the public proving embarrassing
C. past indiscretions, if they were exposed to the public, would prove to be embarrassing
D. their past indiscretions would prove embarrassing if exposed to the public
E. it would prove embarrassing if their past indiscretions had been exposed to the public

Would anyone explain why OA- [spoiler][D][/spoiler] beats my choice [spoiler][C][/spoiler]? Thanks