Lab is a type of Workplace. you are likely to find Union in/at/on Workplace. Union is similar to Closed. 
Sight is the opposite of Sound. Sound is related to Human. Arab is a type of Human. 
Lab --IsA--> Workplace <--AtLocation-- Union <--SimilarTo--> Closed 
Sight <--Antonym--> Sound <--RelatedTo--> Human <--IsA-- Arab 