Correct Answer - A
The energy band scheme of semiconductors is shown here.
In semiconductors, valence gap called the forbidden energy gap. It is vely small. At room temperature some electrons in valence band acquire thermal energy. this energy is more than forbidden energy gap `E_(g)`, thus they jump into the conduction band and leave their vacancy in the valnce band which act as holes. Hence, at room temperature valence band is partially empty and conduction band is partially filled.
