The correct answer is A) by a separate treaty.
The United States acquired Florida from Spain by a separate treaty.
The Florida Purchase Treaty of 1819 is also known as the Adams.Oni Treaty. It was signed on February 22, 1819, between Spain and the United States. Spain had faced many problems in sending settlers to Florida. And it represented a conflict for the European country. The treaty was signed by the United States Secretary of State John Quincy Adams and the Spanish Minister, Luis de Odonis.