This is one of those that is so completely context-dependent that I don't even think I can give it a grade? If it's something like what you write, then A. But there's sooooooooooooo much bad a/b/o out there. So much. So much. I will basically only read mpreg at this point if a) it's from an author I already trust or b) the summary is incredibly well-written.

So A in theory but D in practice? If that makes sense?