In Watson’s famous “Little Albert” study, which emotion was he studying

In Watson’s famous “Little Albert” study, which emotion was he studying?  Prior to this study, how did he determine that this emotion was one of 3 “fundamental emotions” and how did he condition this emotional response in little Albert?  Who later demonstrated how to remove this response from little Albert and how did she do it?  What ethical lessons are to be learned from all of this?