The correct answer is B) Germany.
The top flying ace of World War 1 was Manfred Von Richthofen, who hailed from Germany.
Manfred Von Richthofen (1892-1918) was a member of the German Air Force. An outstanding pilot fighter known as the Red Baron for its deeds on air, Manfred was considered the best pilot Germany had in the war. He is granted with more than 80 victories in combat. He was shot down in combat and died on April 21, 1918.
The other options of the question were a) France and C) Great Britain.