Answer : 4. "सांभर साल्ट्स लिमिटेड"
Explanation :

The correct answer is Sambhar Salts Limited. Key Points Central Government Public Sector Undertakings: Hindustan Salts Limited, Jaipur HPCL Rajasthan Refinery Limited Rajasthan Drugs and Pharmaceuticals Limited, Jaipur Rajasthan Electronics and Instruments Limited (REIL), Jaipur Sambhar Salt Limited, Jaipur