In an intrinsic semiconductor at room temperature;

The correct answer is Option (3) → the number of free electrons and the number of holes are equal and non-zero

In an intrinsic semiconductor, there are no impurity atoms. Electrons can be thermally excited from the valence band to the conduction band, creating equal numbers of electrons and holes.

Thus, the number of free electrons and the number of holes are equal and non-zero at room temperature.

Final Answer: the number of free electrons and the number of holes are equal and non-zero