Coal, in its natural state in the seam is usually a material with low permeability and it is formed in layers under:
A. Low pressure and only by supplying oxygen at high pressure
B. Great pressure only
C. Low pressure and only by supplying oxygen at low pressure
D. Great pressure and only by supplying oxygen at low pressure
Answer:B
Coal, in its natural state in the seam is usually a material with low permeability and it is formed in layers under:
A. Low pressure and only by supplying oxygen at high pressure B. Great pressure only C. Low pressure and only by supplying oxygen at low pressure D. Great pressure and only by supplying oxygen at low pressure