Which of the following circuits is reverse - biased ?

Reverse biasing in a PN-junction occurs when an external voltage is applied in such a way that the positive terminal of the voltage source is connected to the N-type semiconductor, and the negative terminal is connected to the P-type semiconductor.

In other words, if the potential of the P-side is less than that of the N-side of the junction, the diode is said to be in the reverse bias condition.

Amongst the given configurations, this is the correct one which indicates the reverse biasing of the diode.