Brain is related to Reading. Reading is related to Enjoy. you would Sing because Enjoy. 
Keep is a type of Grow. Keep is the opposite of Return. Return is part of Tennis. Tennis is related to Roll. 
Brain <--RelatedTo--> Reading <--RelatedTo--> Enjoy <--MotivatedByGoal-- Sing 
Grow <--IsA-- Keep <--Antonym--> Return --PartOf--> Tennis <--RelatedTo--> Roll 