The answer is D because they would have to make quarries just below the surface to mine
Mineral ores much quicker (Quarries- a large hole/pit under ground used to get stone and minerals)
From Grahams Law the rates of effusion of two gases are inversely proportional to the square roots of their molar masses at the same temperature and pressure.
Therefore; R1/R2 = √mm2/√mm1
The molecular mass of Carbon dioxide is 44 g
Hence; 1.8 = √(44/x
3.24 = 44/x
x = 44/3.24
= 13.58
Therefore, the molar mass of the other gas is 13.58 g/mol