Which statement about cast iron is correct in standard materials practice? (Consider composition, manufacture, and typical remelting route.)

Introduction:
Cast iron is an iron–carbon alloy with relatively high carbon content and accompanying impurities (Si, Mn, P, S). The question checks recognition of a compositionally accurate and contextually correct statement.

Given Data / Assumptions:

• Cast irons solidify with graphite or cementite depending on composition and cooling.
• Manufacturing practice commonly involves remelting pig iron with scrap and flux in a cupola or induction furnace.
• Carbon range for cast iron exceeds that of steels.

Concept / Approach:
Cast irons are not “purified” pig iron; instead, they retain higher carbon and are cast into shape. Typical total carbon is about 2–4.5 percent, with silicon often 1–3 percent to promote graphitization.

Step-by-Step Solution:

Verification / Alternative check:
Textbook data tables list typical carbon ranges and standard melting routes (cupola/induction). Casting shops routinely remelt charge mixes to pour into moulds.

Why Other Options Are Wrong:

• A: Suggests purification, which contradicts the retained high carbon nature.
• B: Partly true but not as defining as composition; also many alloys are cast, so this is not unique.
• D: Opposite of common practice; cupola remelting is traditional.

Common Pitfalls:
Confusing cast iron with steelmaking; equating “purifying” with standard remelting; ignoring that composition definition is the clearest differentiator.

Final Answer:
Cast iron generally contains about 2 to 4.5 percent carbon along with other impurities.