Final answer:
The alternative method to measure electric potential at a point C due to a point charge is by using the formula V = kQ/r.
Step-by-step explanation:
The alternative method to determine the electric potential at point C, without moving a test charge, is to use the formula V = kQ/r. This formula applies specifically to the scenario where the electric potential is being caused by a point charge or a spherically symmetric charge distribution, which behaves like a point charge. The variable V represents the electric potential, k is the Coulomb's constant, Q is the charge causing the potential, and r is the distance from the charge to the point where the potential is being measured.