Difficult is related to Challenge. Challenge is related to Trouble. Trouble is a synonym of Worry. 
Account is related to Story. Story is related to Joke. Joke can be Offensive. 
Difficult <--RelatedTo--> Challenge <--RelatedTo--> Trouble <--Synonym--> Worry 
Account <--RelatedTo--> Story <--RelatedTo--> Joke --HasProperty--> Offensive 