Terrain is related to Sand. Sand is related to Dig. 
Regulator is a synonym of Governor. Governor is related to Stay. Stay is a synonym of Staff. Staff is a type of Provide. 
Terrain <--RelatedTo--> Sand <--RelatedTo--> Dig 
Regulator <--Synonym--> Governor <--RelatedTo--> Stay <--Synonym--> Staff --IsA--> Provide 