The correct answer is C: Holes in P-type material and electrons in the N-type material are separated by the applied voltage, widening the depletion region. Why does a PN-junction diode not conduct current when reverse biased is that holes in P-type material and electrons in the N-type material are separated by the applied voltage, widening the depletion region. Reverse bias widens the depletion region, preventing conduction. For amateur radio operators, this is important for semiconductor knowledge. Understanding this helps when working with diodes.