单语范例（未经PONS编辑处理）
The ascocerid shell, or conch, is the thinnest and most fragile of any orthocone or cyrtocone of comparable size., which accounts for their rarity.
en.wikipedia.org Flooding the defensive zone outright was a rarity due to the level of endurance required from the entire team.
en.wikipedia.org It is not always possible to follow the above points, because of the rarity of such frames, and the need for more pleasing appearance.
en.wikipedia.org Due to its rarity in the ancient world, steel was usually recycled, so broken tools, nails and cookwear often provided a ready supply of steel.
en.wikipedia.org There are three uncredited rarities included on the album.
en.wikipedia.org