This is Usman and I am Petroleum and Gas Engineering Graduate, wanted to appear in CSS-2017.

I have opted following Optional subjects and feeling quite comfortable with them as well;

Physics (200)
International Relations (200)
International Law (100)

For rest 100 marks, considering the fact that I have science related back, I felt myself attracted towards;
Punjabi or Geography or any History (most probably USA History)

Can someone please advise and suggest me in choosing one subject as I shall be travelling to Pakistan in next month to purchase books etc..

Thanks in Advance!!!