Free is a type of People. People is related to Doctor. 
Race is related to Driver. Driver is the opposite of Passenger. you are likely to find Passenger in/at/on Airport. you are likely to find Jet in/at/on Airport. 
Free --IsA--> People <--RelatedTo--> Doctor 
Race <--RelatedTo--> Driver <--Antonym--> Passenger --AtLocation--> Airport <--AtLocation-- Jet 