The conductivity of a semiconductor increases with increases in temperature because:

Question

$\begin{array}{1 1} \text{number density of free current carries increase } \\ \text{both number density of carries and relaxation time increases } \\ \text{relaxation time increases } \\ \text{Number density of current carries increases , relaxation time decreases , but effect of decrease in relaxation time is much less than increase in number density } \end{array} $