I would also have to say A, B, and C.
Commentary on A: Prior to the printing press, there weren't many copies of books so that would make them expensive.
Commentary on B: Illiteracy was very common in the era that you are studying. Only the wealthy or the religious leaders knew how to read.
Commentary on C: Once people had book and were taught to read they were able to think on their own and not have to believe everything they were told, which meant that religious leaders and possibly some wealthy people lost some power because they commoners knew how to read and it made it harder for the leaders and the wealthy people to take advantage of them.
Hopefully this helps.