In the UPSC mains examination, subjects considered optional can include a wide range of disciplines such as Geography, Political Science, History, Public Administration, and Anthropology. Candidates are allowed to choose from a list of subjects based on their interests and academic background. The selection of optional subjects is crucial as it can significantly influence one’s performance in the mains examination, allowing candidates to demonstrate their expertise and depth of knowledge in chosen areas. This choice can also help in shaping their career paths within civil services.