Thermal Decomposition in Blast Furnace Steps:

• Identify thermal decomposition: a reaction where a single compound breaks down into simpler substances using heat.
• Recall blast furnace process: limestone (CaCO₃) is heated to produce quicklime (CaO) and CO₂ for slag formation.
• Examine each equation: check if it shows a compound decomposing via heat in the furnace context.
• Match to option: select the one fitting decomposition of CaCO₃.

Why B is correct:

• CaCO₃ → CaO + CO₂ represents the calcination of limestone, a thermal decomposition reaction that occurs when limestone is heated in the blast furnace to remove impurities.

Why the others are wrong:

• A: Combustion of carbon, not decomposition.
• C: Synthesis reaction forming slag, not decomposition.
• D: Invalid equation (uses "-" instead of "→"); resembles C but malformed.

Final answer: B