Productive is a synonym of Fat. Fat is related to Energy. Energy is related to Rest. Rest is related to Road. 
Oxygen is related to Molecule. Molecule is a type of Unit. 
Productive <--Synonym--> Fat <--RelatedTo--> Energy <--RelatedTo--> Rest <--RelatedTo--> Road 
Oxygen <--RelatedTo--> Molecule --IsA--> Unit 