Experiment is related to Test. Test is related to Difficult. Difficult is related to Complicated. 
Married is a type of Person. Teacher is a type of Person. Professor is a type of Teacher. 
Experiment <--RelatedTo--> Test <--RelatedTo--> Difficult <--RelatedTo--> Complicated 
Married --IsA--> Person <--IsA-- Teacher <--IsA-- Professor 