Explanation:

Jamnagar in Gujarat is the largest petrochemical industrial center of India.The city is famous for the petrochemical industry due to the presence of Reliance Ltd which is the biggest petrochemical industry in India at present.The industry is essential for the growth of other sectors such as textiles, power, cables, telecom, plastics, etc.The other centers include Mumbai, Mettur, Mathura, Pimpri, Barauni, etc. The first one was set up in 1961 in the city of Mumbai.