srij13
I am confused between C and E.
I'd look at the problems with C in two ways:
1) The meaning is off. When you include the "as factors" caveat, you're attributing "as factors" as an important part of how they contribute. For example if you say "As a university employee, you can receive free tuition for your immediate family" -- there "as a university employee" is integral to your ability to receive tuition. Or "Stacy was able, as CEO, to turn the company's fortunes around" -- that means she did that as CEO, not in a previous capacity as VP or Director of Ops or whatever.
So...when C says "are able to contribute as factors to..." it's assigning extra value to "as factors" as integral to how high cholesterol or unbalanced homocysteine contribute heart disease. Which doesn't really make sense..."factors" is kind of a placeholder definition - whether or not we give them that designation doesn't really matter as to whether they can contribute to heart disease.
2) Redundancy. If they're contributing to heart disease, then they're automatically factors that lead to heart disease...we don't need to call that out specifically (especially because of point #1 - calling it out specifically creates a strange meaning). E says the same thing more concisely without that redundancy, and therefore has a much cleaner, more precise meaning.