Electrical conductivity of insulators is

Which of the following graphs represents the temperature $(T)$ dependence of resistivity $(\rho)$ of a semiconductor?

Resistivity of a semiconductor depends on

Choose the correct statement. In semiconductors,the valence band and conduction band

If $V_0$ is the volume of a standard unit cell of germanium crystal containing $N_0$ atoms, then the expression for the mass $m$ of a volume $V$ in terms of $V_0, N_0, M$ and $N_A$ is [here, $M$ is the molar mass of germanium and $N_A$ is the Avogadro's constant].

Why is the motion of an electron in a solid different from that in an isolated atom?