Explanation:

Conservation categories are used to classify the status of wildlife species based on their risk of extinction. These categories help in identifying and prioritizing conservation efforts for different species. The four main conservation categories are extinct, endangered, endemic, and vulnerable.

A) Extinct:
The category of extinct is used to describe species that no longer exist in the wild or anywhere else on the planet. These species have completely disappeared and have no living individuals.

B) Endangered:
The category of endangered is used to describe species that are at a very high risk of extinction. These species have a small population size and face various threats, such as habitat loss, poaching, climate change, or pollution.

C) Endemic:
The category of endemic is used to describe species that are found only in a particular geographic area and are not naturally found anywhere else. These species are unique to a specific region and are often vulnerable to habitat destruction or changes in their limited range.

D) Vulnerable:
The category of vulnerable is used to describe species that are at a lower risk of extinction compared to endangered species but still face significant threats. These species have a larger population size than endangered species but are still susceptible to habitat loss, hunting, or other factors that may lead to their decline.

Therefore, the correct answer is D) Vulnerable as it is indeed a conservation category of wildlife.