The correct option is A Western Ghats
The biodiversity hotspots in India are the Himalayas, the Indo-Burma region and the Sundaland [Includes Nicobar group of Islands], The eastern ghats receive lesser rain when compared to the western ghats so the biodiversity is higher in western ghats and is considered as a hotspot.
The Indo-Gangetic plains are large alluvial plains which makes it a fertile land. Thus it is highly populated by humans.
Aravalli hills are sacred groves - Sacred groves are forest fragments of varying sizes, which are communally protected, and which usually have a significant religious connotation for the protecting community.