The correct answer is "France's King Phillip Vl snatched land from King Edward III and retaliation had to follow".
When King Charles IV of France died, there was uncertainty over who had to be his successor, as there was a principle within the kingdom of France that a woman could not be heir to the throne. Therefore, Isabella of France, sister of Charles IV alleged that the rightful successor was King Edward III of England. This claim was neglected by the French and they subsequently named Philip, Count of Valois, who was the cousin of Charles IV, as king of France.
After a series of disagreements between the 2 Kings, Philip VI decided to confiscate lands that belonged to Edward III. This caused Edward III to reassert his claim of being King of France and the 100 Years War started.