The correct answer is D) remotely open and close contacts by action of a coil. An electromagnetic relay is most commonly used to remotely open and close electrical contacts by the action of an electromagnetic coil. When the coil is energized, it creates a magnetic field that pulls the relay's contacts together, completing the circuit. When the coil is de-energized, the contacts open, breaking the circuit. This allows for remote control and switching of electrical circuits, which is a primary function of electromagnetic relays. The other answer choices are incorrect because they do not accurately describe the most common use of an electromagnetic relay. Relays are not typically used to provide capacitance, inductive power, or overcurrent protection in a circuit.