The correct answer is option 1, II Five Year Plan. The iron and steel industries at Bhilai, Durgapur, and Rourkela were established during the second Five Year Plan. The Five Year Plans were a series of economic development initiatives implemented by the Indian government after independence. The second Five Year Plan spanned from 1956 to 1961, and during this period, the government focused on industrialization and the development of heavy industries. Bhilai, Durgapur, and Rourkela were chosen as locations for large-scale iron and steel plants to meet the growing demands of the country. These industries played a significant role in the industrialization of India and contributed to its economic growth.