PV = nRT
PV = $\frac{w}{M} \, RT$
$\frac{PM}{RT}$ = d
(A) d = $\frac{1 \, atm \times M}{R \times 273 \, K}$
(B) d = $\frac{2 \, atm \times M}{R \times 273 \, K}$
(C) d = $\frac{1 \, atm \times M}{R \times 546 \, K}$
(D) d = $\frac{2 \, atm \times M}{R \times 546 \, K}$
$d$ will be minimum when numerator is minimum and denominator is maximum. Thus, (C) is the correct choice for the answer.