Hi varsh! Well if you have taken PCB in your 12th std than you can either proceed with the science as a domain and then later focus on UPSC because there exist a selection of optional subject which you can choose physics,  biology or whatever you want. The other way is that if you are really ambitious about UPSC than you can go with B.A. hons with economics,  as it is a great option, or you can take geography, political science,  history as BA subjects.  Choose whatever works best for you.

Hope this will help you!