Greetings candidate,

It really depends upon the interests you have and the career you want to pursue. If you want to a pursue a career in technical profession, you should choose PCM. PCM will involve mathematics as one of the primary subject. So you can take PCM if you consider yourself to be good in mathematics. If you want to pursue a career in medical profession, you can take PCB which involves Biology as one of the primary subject. PCB involves only basic mathematics of junior level but there goes a lot of theory in Biology. So it totally depends upon you in the end. Good luck.

Yes, you can. You need to have standard mathematics only for opting mathematics at higher level... Other than that you can choose your subjects. However, I would highly recommend you to not go for pcb since it will be really tough for you and will involve a lot of maths. If you are not good at maths, it's better to not go for science courses.