A zener diode is always ___________ connected.

Answer: Option A

A zener diode is a type of diode that is designed to operate in the reverse breakdown region of its voltage-current characteristic curve.

Reverse (Option A) is the correct answer because zener diodes are primarily used in reverse bias configuration where they maintain a constant voltage across their terminals when the voltage exceeds the breakdown voltage (zener voltage). This characteristic makes them useful for voltage regulation and protection in electronic circuits.

Option B: Forward is incorrect because while diodes in general can conduct in the forward bias mode, zener diodes are not typically used in this mode for their intended purpose.

Option C: Either reverse or forward is incorrect because zener diodes are specifically designed and optimized for operation in the reverse bias mode.

Option D: None of the above is incorrect because zener diodes are indeed always connected in the reverse bias configuration for their intended applications.

Therefore, the correct answer is reverse.