Condition is a type of Teach. Condition is related to Dry. Desert can be Dry. 
Helpful is related to Hand. Hand is related to Soap. Soap is related to Opera. 
Teach <--IsA-- Condition <--RelatedTo--> Dry <--HasProperty-- Desert 
Helpful <--RelatedTo--> Hand <--RelatedTo--> Soap <--RelatedTo--> Opera 