In blast-furnace ironmaking and basic smelting chemistry, identify the correct chronological set of reactions driven by the combustion of fuel inside the furnace. Choose the most comprehensive statement that reflects what actually happens to CO2, CO, and iron oxides during smelting.

Introduction / Context:
Smelting in a blast furnace relies on a sequence of gas–solid reactions. Fuel burns to generate heat and gases, those gases are then chemically transformed, and finally the reduced gas species convert iron oxide to metallic iron. This question checks whether you understand the standard reaction chain that turns coke and air into a reducing environment for iron ore.

Given Data / Assumptions:

• Fuel is mainly coke (carbon) with hot air blast.
• Iron ore is primarily hematite Fe2O3 (representative iron oxide).
• Typical high-temperature zones foster both combustion and gas–solid reactions.

Concept / Approach:

The reaction pathway is well established: carbon burns to form CO2; that CO2 reacts endothermically with hot excess carbon to form CO; and CO is the principal reducing gas that converts Fe2O3 to Fe while regenerating CO2. This establishes a CO/CO2 loop that continuously reduces fresh oxide descending through the stack.

Step-by-Step Solution:

Verification / Alternative check:

Mass and energy balances in furnace models reproduce this cycle. Gas sampling in furnace uptakes confirms high CO content consistent with ongoing indirect reduction.

Why Other Options Are Wrong:

Only (a) and (b): incomplete because it ignores the critical reduction of Fe2O3 by CO. Selecting any single step misses the integrated cycle that makes smelting viable.

Common Pitfalls:

Confusing direct reduction by solid carbon with dominant indirect reduction by CO in the furnace shaft; assuming CO2 itself reduces oxides efficiently (it does not).

Final Answer:

All the above