John Green, in his discussions about the French and Indian War, primarily emphasizes economics as the principal cause of the conflict. He highlights that the British and French were competing for control over lucrative territories in North America, driven by mercantilist interests in gaining access to raw materials and trade routes. This competition for land and resources ultimately led to the war, as both colonial powers sought to expand their influence and control over the region. Therefore, the correct answer from the options you provided would be:
Economics -- gaining raw materials through territorial gains (mercantilism).