The industry that forms the base for all other industries is _____.

Iron and steel industry

The correct answer is Option (3) → Iron and steel industry

The iron and steel industry forms the base of all other industries and, therefore, it is called a basic industry. It is basic because it provides raw material for other industries such as machine tools used for further production. It may also be called a heavy industry because it uses large quantities of bulky raw materials and its products are also heavy.