The valence band and conduction band of a solid overlap at low temperature. The solid may be:

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

At absolute zero,$Si$ acts as

The temperature dependence of resistances of $Cu$ and undoped $Si$ in the temperature range $300-400 \ K$ is best described by:

Pure sodium $(Na)$ is a good conductor of electricity because the $3s$ and $3p$ atomic bands overlap to form a partially filled conduction band. By contrast,the ionic sodium chloride $(NaCl)$ crystal is:

Which of the energy band diagrams shown in the figure corresponds to that of a semiconductor?