The correct answer is B: Emitter.

In the common emitter (CE) configuration, the emitter terminal is common to both the input and output circuits — hence the name.

• Input: Applied between the base and emitter terminals.
• Output: Taken between the collector and emitter terminals.
• A small base current controls a much larger collector-to-emitter current, enabling amplification.

Advantages of Common Emitter Configuration:

• High voltage gain — suitable for amplification applications.
• High current gain — efficient control of output current with small input current.
• Inverts the input signal (180° phase shift).

Disadvantages:

• Lower input impedance compared to common base or common collector configurations.
• Relatively high output impedance.

Applications:

• Audio and radio frequency amplifiers.
• Digital switching circuits.