The correct option is The vast sandy expanse.
Explanation
The Great Indian Desert, also known as the Thar Desert, is located to the northwest of the Aravalli Hills. Physiographically, the Rajasthan Plain is divided into two distinct regions: the Marusthali and the Rajasthan Bagar.
Detailed Analysis
- Marusthali: The term literally translates to the "Land of the Dead." It refers to the vast sandy expanse constituting the desert proper. This region is characterized by extreme aridity, sparse vegetation, and extensive sand dunes. It occupies the western part of the Rajasthan Plain.
- Rajasthan Bagar: This is the semi-arid transitional plain located between the Aravalli Range in the east and the sandy Marusthali in the west. It is relatively more fertile and supports steppe vegetation.
Therefore, the term 'Marusthali' is specifically used to describe the sandy desert region.
Key Takeaway
Marusthali is the core arid region of the Thar Desert characterized by shifting sand dunes and low rainfall, distinct from the semi-arid Bagar region.