Necessary is the opposite of Impossible. Impossible is related to Movie. Movie is related to Ring. you are likely to find Diamond in/at/on Ring. 
Air is related to Current. Current is related to Contemporary. 
Necessary <--Antonym--> Impossible <--RelatedTo--> Movie <--RelatedTo--> Ring <--AtLocation-- Diamond 
Air <--RelatedTo--> Current <--RelatedTo--> Contemporary 