A p-n junction can act basically as

Both Half as well as full wave rectifier

The correct answer is Option (3) → Both Half as well as full wave rectifier

In a half wave rectifier, a single p-n junction diode allows current to pass only during one half of the input AC cycle, blocking current in half.

In a full wave rectifier, two or more p-n junctions allow current to pass during both halves of the AC cycle, thus providing a smoother DC circuit.