Solution:

At absolute zero temperature (0 K), intrinsic germanium and silicon behave like insulators due to the following reasons:

1. No Free Charge Carriers: At absolute zero, all the electrons in the material occupy the lowest energy states, and there are no thermally excited electrons available to conduct electricity. This means there are no free charge carriers (electrons or holes).
2. Wide Band Gap: Both germanium and silicon have a band gap (about 0.66 eV for germanium and 1.1 eV for silicon). At absolute zero, the thermal energy is insufficient to excite electrons across this band gap from the valence band to the conduction band.

As a result, intrinsic germanium and silicon cannot conduct electricity at absolute zero, behaving as insulators.