Which two pieces of evidence support the idea that the supply of coal is at risk?
A. Only five percent of the available coal is mined and used for various purposes, and its lower portions are wasted.
B. Anthracite coal will run out in fifty years and bituminous coal will run out in less than two hundred years.
C. America has the richest portion on Earth with respect to coal and it needs to conserve it for future generations.
D. Coal fields in only two states, Iowa and Missouri, are already exhausted and coal is used conservatively.