A p-n junction diode is said to be forward-biased when its p-side (anode, represented by the triangle) is connected to a higher potential and its n-side (cathode, represented by the line) is connected to a lower potential ($V_p > V_n$). Although the specific circuit diagrams are missing from the given text, the correct option (Option 4 in the standard AIPMT 2006 paper) depicts a scenario where the potential at the p-side is greater than the potential at the n-side (for instance, p-side at $0 \text{ V}$ and n-side at $-2 \text{ V}$).