The most easily oxidized coal is (). A: lignite coal B: bituminous coal C: lean coal D: anthracite coal

Which of the following is not a common way for coal caving? ( ) A: Top caving coal in group sequence B: Top caving coal in single cycle sequence C: Top caving coal in multiple cycles in sequence D: Top caving coal in intervals of single cycle

The coal industry is running down as coal is gradually replaced by oil.( industry )

The dry ash free volatile content of a coal is 7%, which is most likely to belong to (). A: Bituminous coal B: Anthracite C: Lignite D: Lean coal

The dry ash free volatile content of a coal is 47%, which is most likely to belong to (). A: Lignite B: Lean coal C: Anthracite D: Bituminous coal

( ) is not a real coal, but only a precursor. A: Anthracite B: Bituminous coal C: Lignite D: Peat

Inthiscountry,coal     electricity.

Rich in coal, abundant in oil and gas, while coal is the most important basic energy and raw material in China.

During top coal caving mining, the essential cause of top coal crushing is ( ). A: softening of water in roof strata B: the stress it beared is large than its own strength C: the gas in the top coal expands, leading to breakage D: cracks produced by raw coal during its formation

(   ) is not a real coal, but only a precursor.