B. the Battle of Saratoga
Burgoyne surrendered October 17, 1777. It showed the French that we might have a chance of wining the war,therefore, we earned their support and financial aid.
The battle was lost earlier when 1500 troops went over to Bennington, Vermont to "requisition supplies" They got badly beaten August 17th as did 600 reserve troops sent as reinforcements. Few returned to Saratoga. So a British force that needed to be strengthened was made far weaker setting the British up for the loss at Saratoga.