In India, the steel production industry requires the import of coking coal. Coking coal is a vital ingredient in the production of steel and is used in the process of converting iron ore into iron and then further into steel. India does not have abundant reserves of high-quality coking coal and, therefore, relies on imports to meet its requirements for steel production.

Saltpeter (potassium nitrate) and rock phosphate are not directly related to the steel production process. Saltpeter is mainly used as a fertilizer and in the production of explosives. Rock phosphate is a source of phosphorus used primarily in the production of fertilizers. While these materials may have other industrial applications, they are not directly involved in the steel production industry.

So, the correct answer is "coking coal."