There is an exception for a clear mistake. For example, if the answer was "C" and you put "C," but were marked wrong, or the grades were totaled up incorrectly, we will not hesitate to make appropriate adjustments.
I encourage you to put your energy into the next assignment, rather than in conjuring arguments for why past work should be regraded. Most people follow the former course, and I will not undermine them by awarding extra points to "squeaky wheels."
That being said, the T.F.s and I are available during our office hours (or by appointment) to answer any questions you may have regarding the subject matter of the course.