Response is related to Pain. Pain is related to Emotion. 
Sensor is related to Nose. Nose is related to Human. Human is related to City. City is related to Necessity. 
Response <--RelatedTo--> Pain <--RelatedTo--> Emotion 
Sensor <--RelatedTo--> Nose <--RelatedTo--> Human <--RelatedTo--> City <--RelatedTo--> Necessity 