Dear Savita, from 2020, AIIMS will no longer be conducting its entrance examination for admission to its MBBS course. It will be conducted through NEET. For being eligible for NEET, you should have completed your relevant highest qualification, pass all subject and secure a minimum aggregate of 50% in Physics, Chemistry and Biology. It is 50% for General Category, 45% for PWD and 40% for OBC,SC,ST. You can visit the official page for grading threshold for each subject at: https://www.cambridgeinternational.org/programmes-and-qualifications/cambridge-advanced/cambridge-international-as-and-a-levels/grade-threshold-tables/june-2019/