The species (including animals, plants, fungi, etc.) which are vulnerable to endangerment in the near future are known as threatened species. The International Union for Conservation of Nature (IUCN) is the authority on threatened species, and it treats threatened species as a group of three categories, depending on the degree relative to which they are threatened. Those categories are Vulnerable species; Endangered species and Critically endangered species. A critically endangered (CR) species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as facing a very high risk of extinction in the wild. 18 critically endangered species of animals belong to India.
So, the correct answer is '18'.