Cast iron is used for the manufacture of:

We recall the basic sequence of iron-making operations. In a blast furnace the first solid metallic product obtained from iron ore is called $$\text{pig iron}$$. When this pig iron is remelted in a cupola or induction furnace, with only slight refining, we obtain what is commercially termed $$\text{cast iron}$$. Because cast iron still contains a high percentage of carbon (roughly $$2\% - 4\%$$) together with silicon, sulphur, phosphorus and manganese, it can easily serve as the raw stock for further refining.

Now, if we remove almost the entire carbon content from cast iron by oxidative refining (for example in a puddling furnace), we obtain a product that is very low in carbon, fibrous in structure and highly malleable; this product is called $$\text{wrought iron}$$. Thus cast iron is a starting material for the manufacture of wrought iron.

Next, by controlled partial removal of carbon—so that the final carbon content lies between roughly $$0.1\%$$ and $$1.5\%$$—cast iron can be converted into $$\text{steel}$$. Processes such as the Bessemer, open-hearth or basic oxygen convertor all begin with molten cast (or pig) iron and end with steel, showing that cast iron is also a direct raw material for steel.

Finally, by suitable mixing of fresh iron ore, coke and limestone with returns of already produced cast iron, the same blast-furnace route can regenerate $$\text{pig iron}$$ once again. In actual foundry practice a portion of pig iron charge may itself originate from remelted cast iron scrap. Hence cast iron can legitimately be regarded as a constituent in the manufacture of pig iron too.

Putting these observations together we see that cast iron is utilised in the making of $$\text{wrought iron}$$, $$\text{pig iron}$$ and $$\text{steel}$$.

Therefore, among the given alternatives, the description that fits is:

Option C: wrought iron, pig iron and steel.

Hence, the correct answer is Option 3.