Explanation
- A
Pliocene
Pliocene is a Neogene epoch (about 5.3–2.6 million years ago) of cooler climate and early hominins. It is not the keyed span of the Thar’s surface sands. Using Pliocene here dates the desert’s present cover too far back.
- B
Paleocene
(b) Official key: This paper keys the Rajasthan or Thar desert as an expanse of Paleocene deposits. Paleocene is the first Cenozoic epoch after the Cretaceous. Among the four geological labels, Paleocene is the stored official answer.
- C
Pleistocene and recent deposits
Pleistocene and recent (Holocene) sands and alluvium are the usual textbook description of Thar surface deposits. They are not the official key of this paper. Do not substitute the common geomorphology phrase for the keyed epoch.
- D
Oligocene
Oligocene is a Paleogene epoch of early ice-sheet growth, not the keyed label for the Thar expanse. It sits between Eocene and Miocene and does not match the stored answer.
Summary. Official key is (b). The question asks of which deposits the Thar or Rajasthan desert is the expanse. The Commission keyed Paleocene, not Pliocene, Oligocene, or the familiar Pleistocene-and-recent pairing. Keep the stored letter even when a physical-geography book stresses late Quaternary sands. Neighbouring Cenozoic names are distractors. The official choice is Paleocene.