The word 'Denisovan' is sometimes mentioned in media in reference to

1. A

   fossils of a kind of dinosaurs

   (a) Fossils of a kind of dinosaurs. Denisovans are hominins, not dinosaurs. Not the key.

2. B

   an early human species

   (b) An early human species (Denisova hominins), known from Denisova Cave in the Altai and later from the Tibetan Plateau. That is the official key.

3. C

   a cave system found in North-East India

   (c) A cave system in North-East India is not what the word denotes. Not the key.

4. D

   a geological period in the history of Indian subcontinent

   (d) A geological period of the Indian subcontinent is not the meaning. Not the key.

Summary. Official key is (b). Denisovans are an extinct archaic human population, sister to Neanderthals, identified from DNA and sparse fossils. They are not dinosaurs, not an NE Indian cave name, and not a geological age. Honour (b).