Besides engineering background, you are not bound to go after subjects like environmental sciences, if IF, you are not interested in it......
My advice would be go through the syllabus of all the optional subjects, it won't take much time, but its worth it.... If you are choosing History of USA just because you are curious about history, I would rather suggest History of Indo Pak, because it sets grounds for more insights while dealing with compulsory subjects of Pakistan Affairs and Current Affairs..... These three subjects have two things common in terms of syllabus, Pakistan & India.... Gender Studies is much more easy subject then assumed. I have had opted this subject twice. Go for regional language of punjabi, only if you have grip on it.... and certainly make your decision after having gone through syllabus of that particular subject in comparison with other potential subjects.