Music appreciation the early twentieth century. bartók decided to leave hungary during                a.  world war i.      b.  the late twentieth century.      c.  the french revolution.      d.  the impressionist movement.

The best answer is A) World War 1

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.