Fill in the blanks :
(a) Pig iron in manufactured by using ____ furnace.

Explanation

**Step-by-Step Solution:**

1. **Identify the Type of Furnace Used for Pig Iron Production:**
- Pig iron is primarily produced in a specific type of furnace that is designed for high-temperature operations and the reduction of iron ores.

2. **Determine the Correct Furnace:**
- The furnace used for the production of pig iron is known as a "blast furnace." This furnace utilizes coke as a reducing agent to convert iron oxides into iron.

3. **Understand the Reaction Process:**
- In the blast furnace, coke reacts with oxygen to produce carbon dioxide (CO2) and carbon monoxide (CO). The carbon monoxide then reacts with iron(III) oxide (Fe2O3) to produce iron (Fe) and carbon dioxide.

4. **Write the Reaction Equation:**
- The overall reaction can be summarized as follows:
\[ \text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2 \]
- This equation shows that iron(III) oxide reacts with carbon monoxide to yield iron and carbon dioxide.

5. **Conclude the Answer:**
- Therefore, the complete answer to the fill-in-the-blank question is: "Pig iron is manufactured by using **blast furnace**."

**Final Answer:**
(a) Pig iron is manufactured by using **blast furnace**.

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