Operational guidance for carbon/graphite refractories: select the correct statement regarding the preferred furnace atmosphere and behavior.

Introduction / Context:
Carbon and graphite refractories are widely used where contact with molten iron/steel and slags occurs (e.g., blast-furnace hearths). Their behavior depends strongly on furnace atmosphere and wetting chemistry.

Given Data / Assumptions:

• Carbon oxidizes in strongly oxidising atmospheres at high temperature.
• Carbon is generally non-wetting to molten iron and many slags.
• Dimensional stability is good; large shrinkage is not typical.

Concept / Approach:
Because oxidation damages carbon, these refractories are preferred in neutral or reducing atmospheres. Their low wettability helps resist skull formation and infiltration. Statements implying strong oxidation exposure or high shrinkage are misleading for standard use cases.

Step-by-Step Solution:
Exclude claims of wetting (carbon is generally non-wetting).Select the neutral/reducing atmosphere guidance as correct.Reject high-shrinkage and universal slag-corrosion claims as inaccurate generalizations.

Verification / Alternative check:
Design notes for BF hearths and ladles emphasize protecting carbon from oxidation while leveraging its non-wetting behavior.

Why Other Options Are Wrong:
(a) Opposite of typical behavior; (c) and (d) overstate issues; (e) contradicts best practice.

Common Pitfalls:
Overlooking atmosphere control; even small oxygen ingress accelerates carbon loss.

Final Answer:
They should be used in neutral or reducing atmosphere.