Which of the following describes a three-terminal voltage regulator?

A three-terminal voltage regulator, such as the widely used 7805 or LM317, acts as a series regulator. In this configuration, the regulator's internal pass transistor is placed directly in series between the unregulated input voltage source and the load. It regulates the output by continuously adjusting its internal resistance to drop the excess voltage, ensuring the load receives a constant voltage. This is fundamentally different from a shunt regulator, which is placed in parallel with the load and regulates voltage by shunting excess current to ground. Because these devices are specifically designed to output a stable voltage rather than a stable current, the distractors identifying them as "current sources" are incorrect.