The Galvanic cells will behave like an electrolytic cell when

$E_{cell} < E_{ext}$

The correct answer is Option (3) → $E_{cell} < E_{ext}$

A galvanic cell generates a spontaneous electric current due to a positive cell potential ($E_{cell} > 0$), driving electron flow from anode to cathode. However, if an external potential ($E_{ext}$) is applied in opposition to the cell's natural potential, the behavior changes:

• When $E_{cell} < E_{ext}$, the external potential exceeds the cell's natural potential, reversing the spontaneous reaction. This forces the cell to operate as an electrolytic cell, where an external power source drives a non-spontaneous redox reaction (electrons are pushed in the opposite direction).

Why others are incorrect:

• $E_{cell} = 0$: At equilibrium, the cell stops functioning as either a galvanic or electrolytic cell (no net reaction occurs).
• $E_{cell} > E_{ext}$: The cell continues to function as a galvanic cell, as its natural potential overcomes the external opposition.
• $E_{cell} = E_{ext}$: The system is at a balance point, with no net current flow (neither galvanic nor electrolytic behavior dominates).