Wheat is a type of Plant. Plant is a type of Stock. Stock is related to Market. you are likely to find Onion in/at/on Market. 
Ought is related to Do. Do is a synonym of Finish. Finish is the opposite of Initiate. Initiate is the opposite of End. 
Wheat --IsA--> Plant --IsA--> Stock <--RelatedTo--> Market <--AtLocation-- Onion 
Ought <--RelatedTo--> Do <--Synonym--> Finish <--Antonym--> Initiate <--Antonym--> End 