The correct answer is C. "George Washington led his army to a decisive victory at Yorktown." This sentence best supports the main idea because it directly relates to George Washington's leadership during the American Revolution. The sentence highlights his military leadership by mentioning his role in leading the army to a decisive victory at Yorktown. This supports the main idea that George Washington showed great leadership during the American Revolution.
Option A, "George Washington was born in 1732," is not the best choice because it provides information about George Washington's birth year, which is not directly related to his leadership during the American Revolution.
Option B, "George Washington served as an officer during the French and Indian War," is also not the best choice as it provides information about his involvement in the French and Indian War, which is not directly related to his leadership during the American Revolution.
Option D, "George Washington lived in Mount Vernon with his wife, Martha," does not support the main idea because it provides information about where George Washington lived and his relationship with his wife, Martha, which is not directly related to his leadership during the American Revolution.
Therefore, option C is the best choice as it directly supports the main idea by highlighting George Washington's leadership during the American Revolution through his decisive victory at Yorktown.