The correct response is:
They had been forced out of the North.
In 1779, the British decided to focus on the Southern colonies primarily because they had suffered significant losses in the Northern campaigns, particularly after events like the Battle of Saratoga, which had galvanized support for the American cause, including French support for the Americans. The British believed that the Southern colonies had a higher concentration of loyalists who could support them and that they could regain control in that region.