Online is the opposite of Print. Machine can be used for Print. 
Lecture is related to Professor. Professor is the opposite of Student. Student is related to Debt. Debt is related to Bill. 
Online <--Antonym--> Print <--UsedFor-- Machine 
Lecture <--RelatedTo--> Professor <--Antonym--> Student <--RelatedTo--> Debt <--RelatedTo--> Bill 