Correct Option
Coking coal is a critical raw material for steel production, particularly through the blast furnace method. India possesses limited reserves of high-grade coking coal suitable for metallurgical purposes. Consequently, the Indian steel industry heavily relies on imports, primarily from countries like Australia, Canada, and the United States, to meet its requirements. A significant portion of India's steel output depends on imported coking coal.
Incorrect Options
Saltpetre (potassium nitrate) is historically associated with the production of gunpowder and explosives, and is also used as a fertilizer. It is not a primary raw material required for steel manufacturing.
Rock phosphate is a key raw material in the production of phosphatic fertilizers and phosphoric acid. It does not play a role in the steel production process.
Given that only coking coal among the listed options is essential for India's steel production industry, option (D) is incorrect.