这类古董因其稀有性而备受珍视。

Such antiques are highly valued due to their ___rarity.

具有重大历史意义的物品因其稀缺性而变得无价。

Items of great historical significance are priceless because of their ___rarity.

某些鸟类物种日益稀少，这是环保人士严重关切的问题。

The increasing ___rarity of certain bird species is a serious concern for conservationists.