Why Correct: Karst topography forms in soluble carbonate rocks like limestone or dolomite through dissolution by groundwater. Jalpaiguri district in West Bengal contains the Buxa and Jainti hills with extensive limestone deposits that develop karst features such as sinkholes, caves, and underground drainage.
Distractor Analysis: Purnea district in Bihar lies in the Gangetic alluvial plain with no significant limestone formations. Jaisalmer region in Rajasthan has arid desert conditions with sandstone, which is non-soluble and does not form karst. Mysore hills in Karnataka consist mainly of granite and metamorphic rocks that are non-soluble and resistant to karstification.
Takeaway: Other prominent karst regions in India include the limestone areas of Meghalaya (Cherrapunji-Mawsynram belt), parts of Madhya Pradesh (Panna), and the Eastern Ghats in Andhra Pradesh.