The correct option is D Western Ghats
A biodiversity hotspot is a biogeographic region with a significant reservoir of biodiversity, that is under threat from humans.
These areas have large numbers of endemic species those found nowhere else but many of these are heavily threatened by habitat loss and other human activities.
Around the world, 35 areas qualify as hotspots. In India, it hosts 3 biodiversity hotspots: the western ghats, the Himalayas and the Indo-Burma region. Western Ghats in India are under threat due to continuous developmental activities and Doon valley is under threat due to continuous mining activities.
Therefore, the correct answer is option D.