Final answer:
The Hundred Years' War was primarily caused by the rivalry between the English and French monarchies and territorial disputes. The French supporting the Scots in its war against England was not one of the causes.
Step-by-step explanation:
The Hundred Years' War was a conflict between England and France that lasted from 1337 to 1453. The main causes of this war were the rivalry between the English and French monarchies, as well as territorial disputes. Option D, 'The French supported the Scots in its war against England,' is not one of the causes of the Hundred Years' War. While Scotland did play a role in the conflict by allying with France, it was not a direct cause of the war.