In semiconductors, at room temperature

(a)The conduction band is completely empty

(b)The valence band is partially empty and the conduction band is partially filled

(c)The valence band is completely filled and the conduction band is partially filled

(d)the valence band is completely filled

(c)

In semi conductros, the conduction is empty and the valence band is completely filled at OK. No electron from valence band can cross over to conduction band at OK. But at room temperature some electrons in the valence band jump over to the conduction band due to the small forbidden gap, i.e. 1 eV.