Open is the opposite of Cover. Cover is related to Shell. Shell is part of Egg. Egg is related to Cholesterol. 
Purpose is related to Call. Call is related to Cry. Cry is related to Display. Display is a synonym of Indicate. 
Open <--Antonym--> Cover <--RelatedTo--> Shell --PartOf--> Egg <--RelatedTo--> Cholesterol 
Purpose <--RelatedTo--> Call <--RelatedTo--> Cry <--RelatedTo--> Display <--Synonym--> Indicate 