rarity, rare, rarely, raring (#8)
Hello which one is correct in 36?
36 a rarity b rare c rarely d raring

"The container was opened by Liz Barham, the
Museum of London's conservator. She said: "It seems to be an ointment and it
has finger marks in the lid. If this is a sealed Roman container, those are
Roman finger marks. This find is a real (36) ........... . To find finger marks is
very extraordinary - we (37) ........... literally hands with history."
36 a rarity b rare c rarely d raring
Since I see an article a I think a noun should be used.
rare is an adjective meaning not seen or found very often
rarely is an adverb meaning not often
As for the rest it sounds like 'rarity' should work, but I don't remember hearing this word ever in my life.

Question

rarity, rare, rarely, raring (#8)
Hello which one is correct in 36? 
36 a rarity b rare c rarely d raring

"The container was opened by Liz Barham, the 
Museum of London's conservator. She said: "It seems to be an ointment and it 
has finger marks in the lid. If this is a sealed Roman container, those are 
Roman finger marks. This find is a real (36) ........... . To find finger marks is 
very extraordinary - we (37) ........... literally hands with history."
36 a rarity b rare c rarely d raring
Since I see an article a I think a noun should be used.
rare is an adjective meaning not seen or found very often
rarely is an adverb meaning not often
As for the rest it sounds like 'rarity' should work, but I don't remember hearing this word ever in my life.

Answer

Rarity is correct and yes it's a noun used to identify something which is rare.
Primarily used for historical artefacts or collectibles but sometimes also things like animals or plants. 
Eg on seeing a rare bird, someone might say That's a rarity in this country, usually this species stays further south.