Go for public administration. It will help you in understanding beaurecracy and how it works. Not only this you will be able to know about different departments of government that how they work,how different ministries work. Budget making, human resource management, administrative setup etc,and there are many other topics in this subject, these topics will help you in interview. If not Interview,then atleast in other papers like Pakistan affàirs ,current affairs etc. Subject is a bit dry one but at the end there are a lot of benefits that you will be having at your end.
But this is just a suggestion. It's better to read this subject yourself for two three days, if you find it easy and you think that you have got an aptitude for it ,then go for it. Go through past papers ,see difficulty level of questions,read topics in syllabus. Only after all these things you will be able to know that which subject is suitable for you.

__________________
''Sufficient for us is Allah , and He is the best Disposer of affairs" Al-Quran