Snake is related to River. River is related to Natural. Natural is the opposite of Unexpected. 
Proper is the opposite of Bad. Bad is related to Emergency. Emergency is related to Location. 
Snake <--RelatedTo--> River <--RelatedTo--> Natural <--Antonym--> Unexpected 
Proper <--Antonym--> Bad <--RelatedTo--> Emergency <--RelatedTo--> Location 