A candidate is eligible to choose an optional subject that he has not studied during the graduation or post graduation level. In addition, candidates can write the exam in English or any of the 22 languages listed in the Eighth schedule of the Indian constitution.
However, a student cannot write different papers of the Civil Services Main Examination in different languages.
Candidates are required to choose two optional subjects of their choice for the main examination. However, the following combinations of optional subjects are not allowed.
1. Agriculture and Animal Husbandry & Veterinary Science.
2. Animal Husbandry & Veterinary Science and Medical Science.
3. Anthropology and Sociology.
4. Commerce & Accountancy and Management.
5. Management and Public Administration.
6. Mathematics and Statistics.
7. Of the Engineering subjects, viz., Civil Engineering, Electrical Engineering and Mechanical Engineering – not more than one subject.
8. Political Science & International Relations and Public Administration.
9. Two literature subjects cannot be opted together. Only one of them can be chosen.
Besides, the candidate can also opt for taking the interview in the same national language that he has chosen to write in the Main examination.