b
$\rho=\frac{ m }{ ne ^2 \tau}$
With rise in temperature, number density $(n)$ of electrons and holes increases for semiconductors.
As $m, e, \tau$ are constant
$\rho \propto \frac{1}{ n } \Rightarrow \rho \propto \frac{1}{ T }$ [Rectangular hyperbola]
