The correct answer is C: 4.

A bridge rectifier is a full-wave rectifier that converts AC input to DC output using four diodes arranged in a bridge configuration.

Working Principle:

• Positive half-cycle: Diodes D1 and D2 conduct; D3 and D4 are in reverse bias.
• Negative half-cycle: Diodes D3 and D4 conduct; D1 and D2 are in reverse bias.
• Current always flows in the same direction through the load, producing unidirectional DC output.

Advantages:

• Utilizes both halves of the AC waveform (full-wave rectification).
• Higher output voltage and power than half-wave rectifiers.
• Lower ripple frequency, easier to filter.

Disadvantages:

• Two diodes always in the conducting path cause a voltage drop of ~1.4V (2 × 0.7V).
• Requires four diodes vs. one in a half-wave rectifier.

Applications: Power supply circuits, battery chargers, and AC-to-DC conversion in electronic equipment.