Nernst equation allows us to make certain predictions about

Correct option is C

✅ (c) Equilibrium concentrations of ions inside the cell when ion transport is due to facilitated diffusion • The Nernst equation calculates the equilibrium potential for an ion across a membrane. • It relates the intracellular and extracellular ion concentrations under passive/facilitated diffusion. • It determines the membrane voltage at which there is no net movement of ions. • Especially useful for potassium, sodium, and chloride ions in cell physiology.
❌ (a) & (b) • Nernst equation is not restricted to external concentrations only. • Also, it assumes no energy input, so not valid for active transport.
❌ (d) • Ion transport driven by energy (ATP) violates Nernst assumptions (i.e., passive diffusion).