It is not mandatory to choose the same subject that you chose for the graduation while taking up UPSC CSE examination. Graduation is done based on your preferences. You could have specialized in any stream such as humanities, engineering, science, management, or literature. Usually, these are either three or four year courses. Irrespective of this, you can choose any subject for the UPSC examination. There are a slew of factors you need to consider before choosing an optional subject for the UPSC CSE examination. There are a slew of subjects suggested by the UPSC board and these fall between graduation and PG level.