Which of the following expressions correctly represents the constant density ρ \rho\,ρ of the gas, where m m\,m is the gradient of the line and R R\,R is the molar gas constant?
mMR\dfrac{m M}{R}RmM
273.15 mMR\dfrac{273.15\, m M}{R}R273.15mM
mM273.15 R\dfrac{m M}{273.15\, R}273.15RmM
p0MR\dfrac{p_0 M}{R}Rp0M
