Question

________ is the highest quality hard coal.
A. Black coal
B. Gray coal
C. Noncoal
D. Anthracite
E. None of these

Answer 1

Hint- It is a metamorphic rock. It is very similar in appearance to the mineraloid jet and is sometimes used as a jet imitation. The moisture content of this fresh-mined coal is normally lower than 15 percent.
Chemically, it might be considered as a transition stage between ordinary bituminous coal and graphite,

Complete Answer:
Coal is generally classified into four main types, or ranks: anthracite, bituminous, subbituminous, and lignite. Anthracite has the highest quality of hard coal. It is also called hard coal, is a hard, compact variety of coal having a submetallic luster. It has the highest carbon content, the fewest impurities, and the highest energy density of all types of coal and is considered as the highest-ranking of coal. Unlike other types of coal, anthracite is generally considered to be a metamorphic rock. It has a carbon content of more than 87% on a dry ash-free basis. This coal in general has the greatest heating value per ton on a mineral-matter-free basis. Anthracite ignites with difficulty and burns leaving a short, blue, and smokeless flame.

Therefore, option D (Anthracite) is the correct answer.

Note- Since the early 1980s, anthracite refuse or mine waste has been utilized for coal power generation in a way of recycling. The practice known as reclamation is being applied to culm piles antedating laws that require the owners of mine to restore lands to their approximate original condition.
Anthracite is related to strongly deformed sedimentary rocks that were put through higher pressures and temperatures (but short of metamorphic conditions) same as bituminous coal is generally linked with less deformed or flat-lying sedimentary rocks.