There are so many optional subjects for ias mains.i am confused whether to take two or one optional subject?i am an commer ceback ground stu

There are so many optional subjects for ias mains.i am confused whether tp take two or one optional subject? i am a commerce background student.i have secured 60%inssc,70%in12th,70%in degree b.com(computers).i am planning to take public administration as one option.