As optional subject carries around 25% weightage (400/1500), scoring more in optional subject is the key to cracking this examination.  So it’s better to choose optional subject wisely and not to do hurry while choosing it

Major issues faced by an aspirant while choosing an optional subject:

• Ambiguity over there area of interest.
• Confusion over language selection. 
• Resource availability of particular subject.
• Rumors related to certain subjects.
• Difference of opinions from different persons creating confusion over optional selection.

One should go through the following basic guidelines for choosing the correct Optional subject:

• Every optional subject has its own toughness level, so one should not bother about the toughness of that subject; your interest should be the top priority.
• One should go through the detail syllabus of related subject so that you can get some idea about the subject.
• Read some NCERT books of related optional subjects and try to find your interest in particular subject.
• Sometimes an optional subject covers many more parts of General Study’s syllabus (Political science and International Relations, Public administration, Geography etc.). So it would save your time for preparation. (It is more feasible and best option while choosing your optional subject.)
• Those aspirants who did graduation in Engineering can choose respective field related subjects as there optional (Mathematics, Civil Engineering etc.) if you think you are perfect in that subject. Many Engineering students chose Geography as there optional subject but at the end it’s on your own area of interest.
• Many Medical students chose Anthropology, Medical Science as there optional subjects so one should go with their relative fields.
• For aspirants who have specialization in graduation in certain subjects such as Public Administration, Political Science, International Relations, Geography etc. should choose that appropriate subject as there optional.

All above are just suggestions, there are many examples of students who chose the direction against the flow and are successful also. They just stick to their decisions and executed it precisely and properly. So while taking final call what matters is your own interest.