The correct option is B Threatened species
IUCN is the world’s most detailed inventory of global conservation status of species of plant and animals. It provides information about its range, population size, habitat and ecology, use and/or trade, threats and conservation actions.
Red list of IUCN is a step to converse biodiversity and it includes names of all threatened species. Threatened species are the species which are prone to be endangered in near future. For example, red panda.
Therefore, the correct answer is option D.