Avogadro's law, which states that equal volumes of gases under the same conditions of temperature and pressure will contain equal numbers of molecules.
Avagadro's law gives the relationship between volume of gas and number of moles of the gas. When the temperature and pressure are constant, volume is directly proportional to number of moles of gas.

V -volume and n - number of moles of gas.
parameters for the first instance are on the left side and parameters for the second instance are on the right side of the equation
initial number of moles n1 - N
n2 - 2N as the number of moles are doubled
V1 - initial volume - 2.10 L
V2 - final volume - V
substituting the values in the equation

V = 4.20 L
final volume is 4.20 L
The general process for coal mining and refining is option C.
Coal mining is carried out by two main processes based on the depth, quality, thickness, and structure of coal seam. Based on the depth, coal seam of less than 180ft to the surface is surface mined while coal seems between 180ft.-300ft. are deep mined. The coal mined is transported to a nearby processing plant using a conveyor, train, ship, etc. where it is washed to remove other component like dirt, sulphur, rocks, etc. and afterwards dried.
From another answer, it is most likely E. Horizon. Hope this helps!
Answer:
Price ceiling. In order to limit the shortages that naturally result from a price ceiling, the government can do what to certain goods? Ration.
Explanation: