Examination is a type of Investigation. 
Cooperate is etymologically related to Operate. Work is a type of Operate. Specialize is a type of Work. Specialize is a synonym of Narrow. 
Investigation <--IsA-- Examination 
Cooperate --EtymologicallyRelatedTo--> Operate <--IsA-- Work <--IsA-- Specialize <--Synonym--> Narrow 