IIM Kozhikode converted, should I forego the offer and give C (A/B no shot due to lower graduation score) another shot?

The answer depends on your percentage and work experience. 

My personal suggestion would be to forego the offer and give IIM C another chance. This answer is based on personal experience so might not be applicable to everyone. Only forego the offer if:

• You are confident that you can score around 99% again the next year

• You add more work experience in the meantime

The key is that if you are foregoing the offer, use the entire year to acquire new skills, gain work experience and upgrade your CV. The decision will be your own. But make sure you accept the results next year without any regrets.