Answer:
Option 4, conquerable, is the right answer.
Explanation:
During the Second World War, the United States caused an air raid on the mainland of Japan on April 18, 1942. This raid was made in Tokyo, the capital city of Japan and some other places on Honshu. This raid was the first air operation to the mainland of Japan. This attack unveiled that Japan was defenseless to the United States and that Japan was Conquerable. This raid boosts the morale of the Americans.
