Preserve is a synonym of Continue. Continue is a synonym of Retain. Retain is a synonym of Hold. Hold is a synonym of Have. 
Light is related to Emission. Emission is related to Exhaust. Exhaust is a synonym of Use. 
Preserve <--Synonym--> Continue <--Synonym--> Retain <--Synonym--> Hold <--Synonym--> Have 
Light <--RelatedTo--> Emission <--RelatedTo--> Exhaust <--Synonym--> Use 