Hunger would make you want to Buy. Birthday would make you want to Buy. 
Sun is related to System. System is related to Judge. Judge is a synonym of Truth. Truth is related to Answer. 
Hunger --CausesDesire--> Buy <--CausesDesire-- Birthday 
Sun <--RelatedTo--> System <--RelatedTo--> Judge <--Synonym--> Truth <--RelatedTo--> Answer 