Which of the following is commonly used as a visual indicator?

An LED, or Light Emitting Diode, is a type of semiconductor that emits visible light when an electric current passes through it in the forward direction. Because they are highly efficient, long-lasting, and come in various colors, they are universally used as visual indicators on the front panels of radios, power supplies, and other electronic devices. The distractors are all semiconductor devices, but they do not emit light for visual indication. A FET (Field Effect Transistor) and a bipolar transistor are used for amplification and switching. A Zener diode is used for voltage regulation, not for generating light.