Answer : 4. "Sirohi in Rajasthan"
Explanation :

Answer: D) Sirohi in Rajasthan Explanation: A big bed of rock salt with the top portion of the bed containing potash (though not the variety used as ferilizer) has been discovered in Thar Desert at a depth of 100 metres. A massive belt of lead and zinc has been found in the Agucha area, while gold bearing rocks have been discovered in the Tuensang district of Nagaland.