Apology is related to Regret. Regret is related to Should. Should is the opposite of Must. Must is related to Absolute. 
Plant is the opposite of Harvest. Harvest is a type of Remove. 
Apology <--RelatedTo--> Regret <--RelatedTo--> Should <--Antonym--> Must <--RelatedTo--> Absolute 
Plant <--Antonym--> Harvest --IsA--> Remove 