I am going to say that none of these is the fundamental cause of terrorism. I am going to say that it is human nature that is the true core cause of terrorism and that things like economics, religion, and politics are just the things that catalyze our human nature and cause us to act at any given time.
I would argue that human nature causes us to split people into "self" and "other." We define these groups in many different ways. What is important is that we seem to have a need to define them and to feel loyalty to self and potentially to feel hatred towards the other.
Terrorism has been caused by many proximate causes over the years. Religion has caused it, so has politics. So has race and ethnicity. All of these are just the things that bring terrorism to the surface at a given time. The true cause is in our natures.
wow great comment, iv never looked at it that way.