On heating n-type semiconductors -

The correct answer is Option (4) → Both the number of holes and the number of electrons increase equally.

An n-type semiconductor has many electrons from the donor atoms and a few holes. On heating, thermal energy breaks covalent bonds, and each broken bond releases one electron and leaves behind one hole, so electrons and holes are created in pairs.

NCERT (2026-27):
n-type Semiconductor – “… Thus, the pentavalent dopant is donating one extra electron for conduction and hence is known as donor impurity. The number of electrons made available for conduction by dopant atoms depends strongly upon the doping level and is independent of any increase in ambient temperature. On the other hand, the number of free electrons (with an equal number of holes) generated by Si atoms, increases weakly with temperature.”