أنشئ حسابًا أو سجّل الدخول للانضمام إلى مجتمعك المهني.
It is very difficult to say which is important and which is not.
I don't think that a project manage can survive professionally without having reasonably good knowledge and skills in all10 areas of knowledge.
If I am FORCED to pick one, I would suggest 'Project Integration Management'.
Again saying, I am not voting for one area of knowledge only.