The correct answer is C: Transistor. A transistor is the component that can be used as an electronic switch. Transistors can be controlled to switch between on (conducting) and off (non-conducting) states, making them ideal for electronic switching. Transistors are semiconductor devices that can act as electronic switches. When a control signal (base current for bipolar, gate voltage for FET) is applied, the transistor switches on, allowing current to flow. When the control signal is removed, it switches off, blocking current. This switching capability makes transistors essential for amplifiers, digital circuits, power control, and many other applications. Transistors can switch much faster than mechanical switches and can be controlled by small signals.