Science

For IAS, BA would be a better choice.

I think agriculture is the best option because in this field, you have many scopes for job. You can go in the banking field. And, you have many option also. You can check this on Google.
Good luck.

MBA require Graduation in any stream as eligibility criteria. So graduation in which subject is not important. But if you take BBA, then it will be continuation of your graduate studies.
Apart from traditional specializations such as HR, Systems, Marketing and Finance, several sectoral programs also available at MBA like
Media and Entertainment Management
Project Management
Pharma Management
Marine Management
Logistics and Supply Chain Management etc.
If you want to specialize in Agricultural Marketing / Management, it is better to choose B.Sc-Agriculture