Hii!
You haven't specified any details of thr education board in which you appeared or want to apper for re- exam. But, let me tell you that, most of the education boards provide improvement exam options for atleast 2 subjects. So, you can improve.
The Eligibility criteria for pursuing ba llb course states that the Candidate must have passed class 12th with minimum 50% marks in any Subject stream from a recognised Board of education.
Hope this helps.
Good luck!