Intrinsic Semiconductors:
Intrinsic semiconductors are pure semiconducting materials, such as silicon or germanium, that have a balanced number of free electrons and holes at absolute zero temperature. These materials have a band gap between the valence band and the conduction band, which is relatively small. At absolute zero, all the electrons occupy the valence band, and there are no free electrons in the conduction band.

Effect of Temperature:
When the temperature of an intrinsic semiconductor is increased, it leads to the excitation of electrons from the valence band to the conduction band. This excitation can occur through various mechanisms, such as thermal excitation or absorption of photons.

Increased Thermal Energy:
As the temperature increases, the thermal energy of the atoms in the semiconductor lattice also increases. This increased thermal energy provides enough energy for some electrons to overcome the band gap and transition from the valence band to the conduction band. These electrons, once excited, become free electrons in the conduction band.

Electron-Hole Pair Generation:
When an electron is excited from the valence band to the conduction band, it leaves behind an empty space in the valence band called a hole. This hole behaves as a positively charged particle. Thus, the excitation of an electron creates an electron-hole pair.

Increasing Number of Free Electrons and Holes:
As the temperature continues to increase, more and more electrons are excited from the valence band to the conduction band, and consequently, more electron-hole pairs are generated. Therefore, the number of free electrons and holes in the intrinsic semiconductor increases with increasing temperature.

Option A - Increases:
Based on the above explanation, it can be concluded that as the temperature increases, the number of free electrons and holes in an intrinsic semiconductor increases. Therefore, the correct answer is option A - increases.