Which of these components can be used as an electronic switch?

A transistor is a versatile semiconductor component that primarily functions either as an amplifier or as an electronic switch. By applying a small voltage or current to its control terminal (the base or gate), you can turn a much larger current on or off in the main circuit. Unlike mechanical switches that require physical movement from a user or a relay coil, transistors switch states completely electronically. They can do this millions or even billions of times per second, making them the fundamental building blocks of modern digital electronics and computers. The distractors serve entirely different circuit functions. A varistor protects against sudden voltage spikes, a potentiometer is a manually adjustable resistor (like a volume knob), and a thermistor changes its resistance based on temperature.