The potentials are applied to the four p-n junctions as shown below :…

The correct answer is Option (3) → (B), (C) and (D) only

In the diode symbol the triangle (arrow) is the p-side and the bar is the n-side; here the p-side is on the left in every junction. A junction is forward biased when the p-side is at a higher potential than the n-side, \( V_p \gt V_n \).

(A) \( V_p = -5\,\mathrm{V} \), \( V_n = -3\,\mathrm{V} \). The p-side is lower, so it is reverse biased.

(B) \( V_p = 0\,\mathrm{V} \), \( V_n = -3\,\mathrm{V} \). The p-side is higher by 3 V, so it is forward biased.

(C) \( V_p = 7\,\mathrm{V} \), \( V_n = 3\,\mathrm{V} \). The p-side is higher by 4 V, so it is forward biased.

(D) \( V_p = -10\,\mathrm{V} \), \( V_n = -20\,\mathrm{V} \). Since \( -10 \gt -20 \), the p-side is higher by 10 V, so it is forward biased.

So (B), (C) and (D) are forward biased.

NCERT (2026-27):
p-n Junction Diode Under Forward Bias – “When an external voltage V is applied across a semiconductor diode such that p-side is connected to the positive terminal of the battery and n-side to the negative terminal [Fig. 14.13(a)], it is said to be forward biased.”