Most of the books I read are written by people who have been dead for a while and, in most cases, long enough to be in the public domain. So, option A is irrelevant.
Shakespeare is in the public domain. I can purchase a copy of the
Riverside Shakespeare for $91.68... or I can download it for free from MobileRead or Project Gutenberg. While I do love my copy of the Riverside edition for its excellent annotations, I also appreciate that my copy of the free ebook version weighs much much much less. Not having to carry around an 8 pound book is very valuable to me. So, option B, is irrelevant since "value" is a very relative term.
If I wish to have my own copy of a book that is NOT in the public domain--one that I can write notes in and that I don't need to return to the library--than, yes, I'll purchase a copy. I don't really consider it "contributing" to the author (who is most likely dead, remember?). But, if I want something and it has a price tag, well I either pay or I do without. I suppose if we're going to phrase things in terms of right/wrong, C is the closest option, since I haven't really considered shop lifting paperbacks from the local bookstore and, well, stealing is wrong.