As you want to get the details of which subject you must choose in IAS Mains so here is the information of the same for you:

I want to tell you that it all depends on your interest

According to me candidates must take that subject in which he or she has completed his or her graduation as it will be a favorable subject for them

List of optional subjects:
Agriculture
Management
Animal Husbandry & Vetinary Science
Mathematics
Anthropology
Mechanical Engineering
Botany
Medical Science
Chemistry Philosophy
Civil Engineering
Physics
Commerce & Accountancy
Political Science & International Relations
Economics Psychology
Electrical Engineering
Public Administration
Geography
Sociology
Geology
Statistics
Indian History
Zoology
Law

List of Optional Subjects (Literature):
Arabic
Gujarati
Manipuri
Sanskrit
Assamese
Hindi
Nepali
Sindhi
Bengali
Kannada
Oriya
Tamil
Chinese
Kashmiri
Pali
Telugu
English
Konkani
Persian
Urdu
French
Marathi
Punjabi
German
Malayalam
Russian

Contact Details:
Union Public Service Commission
UPSC,
Man Singh Road Area,
New Delhi,
Delhi 110069
India

Map Location: