Detailed Explanation:

Correct Answer: ✅ Option 2

The cement industry is a major contributor to global carbon emissions, accounting for roughly 5–8% of global CO₂ emissions. While both limestone and clay are essential raw materials in cement production, the primary source of CO₂ emissions is the calcination of limestone during clinker manufacturing.

✅ Statement I is Correct: Cement manufacturing contributes more than 5% of global CO₂ emissions, mainly due to clinker production and energy consumption.

✅ Statement II is Correct: Silica-bearing clay is mixed with limestone to provide silica, alumina, and iron oxides required for cement production.

✅ Statement III is Correct: During clinker production, limestone (CaCO₃) is heated and converted into lime (CaO), releasing large amounts of CO₂.

❌ Statement II does not explain Statement I: Mixing clay with limestone is a raw-material requirement and is not the direct cause of significant carbon emissions.

✅ Statement III explains Statement I: The conversion of limestone into lime (calcination) releases CO₂ and is the principal reason for high emissions from the cement industry.

Short Notes: Cement Industry and Carbon Emissions

• The cement industry contributes about 5–8% of global CO₂ emissions.

• The main raw materials are limestone and clay.

• Clinker is the intermediate product used to manufacture cement.

• Calcination reaction: CaCO₃ → CaO + CO₂.

• Around 60% of cement emissions come from the calcination process.

• The remaining emissions mainly come from fuel combustion in kilns.

• Low-carbon cement and carbon capture technologies are being developed to reduce emissions.