Hi

You can choose any subject or course  of your choice based on your interest for your graduation

This is because,

to be eligible for UPSC  examination there is no compulsion to be a graduate in a particular subject, all you need to be eligible is that you should be a graduate in any discipline

So you can choose any stream of your interest, but yes if you choose BA or Arts
then
choosing Arts or the humanities can be really helpful for your UPSC  examination, this is because in Arts you will be learning subjects like history , polity etc which are a part of the UPSC syllabus so it will help you in your upsc examination

Also,

Your UPSC examination has 3 stages which are listed below :-

*The first stage of the exam is Preliminary examination (objective )

*The second stage, Mains (written).

*If you manage to clear both prelims and mains then you are to go through third stage i.e interview/personality test .

And if you managed to clear all the three rounds mentioned above, then congratulations you may become an ias officer

I hope you find this helpful

For detailed information go through

https://competition.careers360.com/articles/upsc-ias-eligibility-criteria/amp

Thank you