Burn is a synonym of Light. Light can be Dark. Dark is related to Bitter. 
Reduce is related to Price. Price is related to Gas. Sky is a type of Gas. you are likely to find Pollution in/at/on Sky. 
Burn <--Synonym--> Light --HasProperty--> Dark <--RelatedTo--> Bitter 
Reduce <--RelatedTo--> Price <--RelatedTo--> Gas <--IsA-- Sky <--AtLocation-- Pollution 