What was it called when 1.5 million African-Americans moved form the south to the north? The great migration

What is the significance of the battle of saratoga? a. the defeat at saratoga allowed the british to invade new england by land. b. after the defeat at saratoga france refuse to sign a treaty with the united states. c. the british won a decisive victory at saratoga. d. after the victory at saratoga france gave open support to the united states including arms money and ships.