Large is related to Small. Small is related to Grain. Grain is related to Individual. 
Reasonable is related to Rational. Rational is similar to Intelligent. Intelligent is the opposite of Dense. Dense is the opposite of Smart. 
Large <--RelatedTo--> Small <--RelatedTo--> Grain <--RelatedTo--> Individual 
Reasonable <--RelatedTo--> Rational <--SimilarTo--> Intelligent <--Antonym--> Dense <--Antonym--> Smart 