Hello,

The eligibility criteria to appear for UPSC CSE is simply passed graduation in any discipline from a recognized university, becoming an IAS officer is dependent on the rank secured by the candidate against his/her respective category, see there is no such thing as best degree/course for appearing in UPSC, only advantage people from humanities stream have is that they are well acquainted with the syllabus as they have continuously studied the subjects at 10+2/graduation level, as there is considerable overlap with general studies and optional subjects, so graduation in subjects like political science/geography/history/public administration/sociology/economics/law to name a few helps in this regard, but if you look at past year toppers they come from as diverse backgrounds as science/commerce/medical/engineering etc, hence it's not the pursuing graduation in humanities stream guarantee that you will qualify this exam, or pursuing other streams proves you will not qualify, personally I believe much more than stream selection it's personal attributes such as single minded focus, dedication, perseverance which help in qualifying this exam which remain the same for all aspirants, hence whatever field you choose you must have interest in that as you'll spend three four precious years of your life, there have been many toppers who are engineering/medical/commerce/science graduates to name a few, prior to appearing for this exam, they have earned experiences in their relative domain, and later on appeared for the exam, also UPSC is highly  competitive and it's good to have a back-up plan also, the rest is up to you, you are the best judge of your choices.