Accident is related to Violent. Violent is the opposite of Peaceful. Peaceful is related to Treaty. Treaty is related to Diplomatic. 
Clock can be used for People. Clock is the opposite of Watch. Watch is related to Danger. Pollution is a type of Danger. 
Accident <--RelatedTo--> Violent <--Antonym--> Peaceful <--RelatedTo--> Treaty <--RelatedTo--> Diplomatic 
People <--UsedFor-- Clock <--Antonym--> Watch <--RelatedTo--> Danger <--IsA-- Pollution 