Hi Alan,
An MBA can be done with any stream of graduation and if you are determined enough you can get through easily. What matters is your interest in the subject. A graduation in Arts will help you get an exposure to various subjects like psychology and economics also.
Whereas a BSc may also provide you with an opportunity to study statistics also which is very helpful in the advanced sectors of HR analytics. And you can work with great firms in HR consulting.
All said and done, in the end, it is your interest in the subjects you take up during your graduation that will improve your knowledge and instill a sense of passion and dedication towards your work.
also, if you can take up subjects like stats, economics, and psychology in Arts that would result in a great combination of required skill sets and help you get brownie points in your application rating score while applying to various colleges like IIM's, TISS, Symbiosis etc.
Hope this helps,
All the best!
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