The important British victory among the options provided is Charleston. The Siege of Charleston in 1780 resulted in a significant defeat for the American forces and was one of the worst American defeats of the Revolutionary War.
Saratoga, on the other hand, was a crucial American victory. Yorktown marked the end of major fighting in the war, but it was also a victory for the American and French forces against the British. Sullivan’s Island was a notable defensive victory for the Americans.