The release of two atomic bombs on Japan in august 1955 helped end World War 11 but ushered in the Cold War, a conflict between the United States and the Soviet Union that dragged on nearly half a century.
The answer should be a) Because the French was lead by Rochambeau and was there at the perfect time. Though c did happen as well, just earlier not during the battle of Yorktown
The battle of Saratoga led to a partnership with the French. By winning this battle, the colonists proved that they could stand their ground and even beat the British.