c
We know that $\rho_{1} V=n R T_{1}$
$\Rightarrow 1 \times V=n R(35+273)$
$=n R \times 308$ $\dots \; (i)$
$\text { and } \rho_{2} V=n R T_{2}$
$\Rightarrow 3 \times V=n R T_{2}$ $\dots \; (ii)$
$\text { On dividing Eq. (ii) by Eq. (i), we get }$
$3=T_{2} / 308$
$\Rightarrow T_{2}=924 K$
$T_{2}=924-273$
$=651^{\circ} C$