Why did spain sell florida to the united states? select all that are true

Hmph.. Spain realized that they could not keep the United States from talking over the Florida territory so in 1819 Spain agreed to sell Florida to the United States. The Adams- Onis Treaty was approved by Spain and the United States in 1821,They were fearful that the United States would go to war with them and they would lose Florida anyway 

I believe your answer is that The United States threatened to declare war otherwise..

Love, grace..-