At absolute zero ($T = 0\,\text{K}$), a pure intrinsic semiconductor behaves like a(n)

1. In a pure (intrinsic) semiconductor, at $T = 0\,\text{K}$ all valence electrons are in the valence band and the conduction band is COMPLETELY EMPTY. 2. With NO carriers available, the semiconductor cannot conduct — it behaves like an INSULATOR. 3. Conduction in intrinsic semiconductors at non-zero $T$ relies on thermal excitation across the small band gap. At $T = 0$ this excitation is impossible. 4. Option A and B require carriers (or paired states) which don't exist at $T = 0$. Option D would require a deliberate trivalent dopant — but the sample is INTRINSIC (pure). _Source: syllabus Physics Part 2, Ch 14, §14.3 (Intrinsic Semiconductor — temperature dependence), p. 4–5._