Final answer:
Option 2: The transistor enters the cutoff region when the base-emitter voltage drops below 0.6 VDC, meaning it does not conduct current between collector and emitter.
Step-by-step explanation:
When the base-emitter voltage of a transistor falls below 0.6 VDC, the transistor will approach the cutoff region. In this region, the base current is so low that it cannot support conducting the collector current, which essentially ceases to flow, meaning the transistor is off and not allowing current to pass from the collector to the emitter. By contrast, the saturation region is where the transistor is fully on, the active region is where it operates as an amplifier, and the reverse bias region typically pertains to diodes rather than the operation of transistors.
When the base-emitter voltage falls below 0.6 VDC, the transistor will approach the cutoff region. In this region, the transistor is effectively turned off and no current flows between the emitter and collector. The base-emitter junction is reverse biased, and the depletion region widens, preventing majority carriers from crossing the junction.