The key subjects included in the UPSC preliminary examination syllabus comprise General Studies Paper I and General Studies Paper II (CSAT). Paper I covers subjects such as Indian History, Geography, Current Affairs, Political Science, and Environmental Science. Paper II (CSAT) evaluates candidates on their comprehension, logical reasoning, analytical abilities, and numerical skills. The diverse nature of these subject areas ensures that candidates possess a well-rounded understanding of essential topics necessary for effective governance and public administration.