What are the different sets of question papers for class 12 board exams, and specifically, what is the meaning of C in OD 14C, OD 15C, OD 16C, etc.?

There are different question papers for Delhi region, all india and for the students who have got a compartment. So you can solve all these papers. There are several publications like arihant which compile all the question papers and provide them to you. I do not know the meaning of C in OD 14c,OD 15c etc.