Which of the following components can supply energy to a circuit?

The ability of a component to supply energy to a circuit is a key factor in understanding how electrical systems operate. A transistor functions as a semiconductor device that can control and amplify electrical signals, acting as a switch or a gate to permit or restrict the flow of current. When used in an active mode, a transistor can supply energy to a circuit by allowing a larger current flowing from a power source to be controlled by a smaller input current.

In contrast, resistors do not supply energy; they dissipate it as heat. Capacitors store energy in an electric field but do not inherently provide energy like a power source does. Inductors store energy in a magnetic field and can influence the current flow but are not designed to supply the energy themselves. Therefore, the correct answer highlights the role of the transistor as a component capable of supplying energy to a circuit, making it essential in various amplification, switching, and signal modulation applications in electronics.