A) A taxon facing an extremely high risk of extinction in the wild in immediate future is known as critically endangered.B) A vulnerable species is one which has been categorized by the International Union for Conservation of Nature as likely to become endangered unless the circumstances that are threatening its survival and reproduction improve.
C) An endangered species is a species which has been categorized as very likely to become extinct.
D) Exotic species, which are also known as alien species, invasive species, non-indigenous species, and bioinvaders, are species of plants or animals that are growing in a nonnative environment.
E) A rare species is a group of organisms that are very uncommon, scarce, or infrequently encountered.
So, the correct answer is 'Critically endangered'.