Bartok was out of the country during World War 1, because he happened to be on vacation in France. Upon his return to Hungary he was deemed unfit for duty, and he spent most of the war travelling around Europe. The time when he truly decided to leave Hungary on a more permanent basis, and due to fundamental disagreements with the Hungarian government, was during World War 2, when he went to the United States to join the war effort against the Nazis.
Not sure if A) should say World War 1 or World War II, but either way, the answer is A.
Bartok was out of the nation amid World War 1, since he happened to be in the midst of some recreation in France. Upon his arrival to Hungary he was esteemed unfit for obligation, and he burned through the vast majority of the war going around Europe. The time when he really chose to leave Hungary on a more lasting premise, and because of basic conflicts with the Hungarian government, was amid World War 2, when he went to the United States to join the war exertion against the Nazis.
