Plea is related to Free. Free is related to Trade. Run is a type of Trade. Fear would make you want to Run. 
Exchange is a synonym of Central. Central is a synonym of Middle. Middle is the opposite of Small. 
Plea <--RelatedTo--> Free <--RelatedTo--> Trade <--IsA-- Run <--CausesDesire-- Fear 
Exchange <--Synonym--> Central <--Synonym--> Middle <--Antonym--> Small 