The simplest way to maintain a potential difference between the two ends of a conductor, so as to get a continuous flow of current is to connect the conductor between the terminals of a _________.

Correct option is D

The correct answer is (d) Battery.
· A battery provides a constant potential difference between its two terminals, enabling the continuous flow of electric current through a connected conductor.
· The chemical reactions inside the battery create an electric potential difference, which drives electrons from the negative terminal to the positive terminal through the circuit.
Explanation of Other Options:
· Voltmeter : Measures the potential difference across a component in a circuit but does not supply any potential difference.
· Ammeter: Measures the electric current flowing through a circuit but cannot maintain a potential difference.
· Rheostat: A variable resistor used to control the current in a circuit, not to maintain a potential difference.