Correct Answer:
C. Anthracite
Coal is formed over millions of years from ancient plant matter under intense heat and pressure, progressing through different ranks. The hardest and highest-rank form of coal used in industries is anthracite. Anthracite is characterized by its high carbon content (typically over 90%), low moisture, and low volatile matter. This composition allows it to burn very cleanly with a high heat output and minimal smoke, making it highly desirable for industrial applications and home heating where efficiency is paramount.
- Peat is the earliest stage of coal formation, not yet true coal, with high moisture and low carbon content.
- Lignite is a low-rank, soft, brown coal with higher moisture and lower carbon than bituminous or anthracite.
- Bituminous is a medium-rank coal, harder than lignite but softer than anthracite, widely used for electricity generation and steelmaking.