Event is related to Reaction. Reaction is related to Fire. Fire is related to Gas. Gas is related to Auto. 
Electronics is related to Charge. Charge is related to Bill. Bill is a type of List. Index is a type of List. 
Event <--RelatedTo--> Reaction <--RelatedTo--> Fire <--RelatedTo--> Gas <--RelatedTo--> Auto 
Electronics <--RelatedTo--> Charge <--RelatedTo--> Bill --IsA--> List <--IsA-- Index 