There is no difference. C series is the old version of ADIS mathematics, and P series is the new version of ADIS mathematics. The old and new versions cannot be mixed. You should have either C 12+C34 or P 1P2P3P4 instead of P 1P2+C34. C34 is the last exam of the old syllabus this year. If you can't finish all the basic math subjects in April, you can't combine your grades. Take p34 for example, c34 is out of date.