Those species whose populations have been seriously depleted and whose ultimate security is not assured are known as

Answer: Option C

Those species whose populations have been seriously depleted and whose ultimate security is not assured are known as vulnerable species.
A vulnerable species is a species that has been categorized by the International Union for Conservation of Nature as being threatened with extinction unless the circumstances that are threatening its survival and reproduction improve.
There are currently 5,196 animals and 6,789 plants classified as Vulnerable, compared with 1998 levels of 2,815 and 3,222, respectively.