Step 1: Define endemism.
A species is considered endemic to a region if it is found naturally only in that specific region and nowhere else in the world.
Step 2: Analyze the species listed.
Option (A) One-horned rhinoceros: Incorrect. While the one-horned rhinoceros is native to India, it is also found in Nepal, making it not strictly endemic to India.
Option (B) Lion-tailed macaque: Correct. The lion-tailed macaque is endemic to the Western Ghats in India and is not found anywhere else in the world.
Option (C) Bengal tiger: Incorrect. Bengal tigers are found in India but also in neighboring countries such as Bangladesh, Nepal, and Bhutan, so they are not endemic to India.
Option (D) Cheetah: Incorrect. The cheetah is not endemic to India. Historically, cheetahs were found in India but are also native to parts of Africa and the Middle East.