Dr Samar,
I personally never believed on scoring/non-scoring theory. Still I'm at sea that how a person can score less in a subject if he have covered it to its depth.
BUt despite my own unwillingness to accept it,statistically it is apparent that zoology is low-scoring,there is little to argue against it. I think it would be unwise for a science student to go for Gender Studies, English or Urdu literature. B/c in those
subjects in which we specialized,we're at home to work with them. Many ppl think that u should opt IR b/c it will help you in Essay, Current & Pakistan affairs. No doubt it does. But your background also counts. For example In CE-2017 6508 appeared in IR but just 1 individual got above 60% marks in it. By seeing the stats, I can bit there will be many ppl who though may've passed all the papers but IR proved the ultimate demon for such unlucky ppl.
So, in nutshell I will say that we've to see our educational background, affinity towards the particular subject shall be looked after in opting the optional subjects