GMAT Sentence Correction (SC) | Re: While some may doubt the feasibility of the proposal

daagh Sir,
Why am i feeling this question is a bit awkward.

Though i understand B is right answer
Due to two reasons
- Either X or Y
- While... because - wrong in E.

My doubt what does it refers to - it can refer to either the feasibility or theproposal.
GMATNinja . ?