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

An LED, or Light Emitting Diode, is a specialized semiconductor device that emits visible light when an electrical current passes through it. Because of their very low power consumption, durability, and long life, LEDs have become the standard choice for visual indicators on nearly all electronic panels and displays. The other components listed are not used for visual indication. A Field Effect Transistor (FET) is an internal component used for signal amplification and switching. A Zener diode is designed to regulate voltage in a circuit. Therefore, the option claiming all choices are correct is also wrong.