A zener diode:

The correct answer is Option (1) → is designed to operate under reverse bias in the breakdown region

A Zener diode is a special p-n junction diode that is used in the reverse breakdown region, where the voltage across it stays almost constant while the current varies widely.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic was removed from the latest NCERT book (2026-27), and it also appears to be out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Zener Diode – “It is a special purpose semiconductor diode, named after its inventor C. Zener. It is designed to operate under reverse bias in the breakdown region and used as a voltage regulator. The symbol for Zener diode is shown in Fig. 14.21(a).”