Offender is a synonym of Criminal. Criminal is the opposite of Policeman. Policeman is derived from Police. 
Level is a synonym of Flat. you are likely to find Flat in/at/on Town. you are likely to find Sign in/at/on Town. 
Offender <--Synonym--> Criminal <--Antonym--> Policeman --DerivedFrom--> Police 
Level <--Synonym--> Flat --AtLocation--> Town <--AtLocation-- Sign 