Concept:In semiconductors, thermal energy at room temperature excites electrons from the valence band to the conduction band.
Explanation:At room temperature, some valence band electrons gain enough thermal energy to cross the band gap.
These electrons enter the conduction band, leaving behind vacant states in the valence band.
Thus, the valence band becomes partially empty because it has holes.
At the same time, the conduction band receives these electrons, so it becomes partially filled.
Therefore, neither band is completely filled nor completely empty in a semiconductor.
Answer:Option D: The valence band is partially empty and the conduction band partially filled.