Hello,

If you're wholly focused on becoming IAS then you should choose humanities stream, as this will help you in your preparation part in the sense you will already be acquainted with subjects such as history, geography, political science, economics etc, as all these are part of UPSC syllabus for GS paper as well as optional and in future if you choose to do graduation in any of the aforementioned subjects, then your subject choice will be aligned with your preparation process, however if you have inclination towards any other career choice, you can go ahead with that also, in general there is no restriction to belong to any stream for upsc exam, candidates from any discipline can appear and diverse backgrounds candidates qualify these exams such as engineering, medical, commerce etc, so in case you want to have a back plan if you're not completely sure at this moment, you can choose it, and later on you can appear for upsc.