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

• A. Incandescent bulb
• B. LED
• C. LCD screen
• D. Photoresistor

Answer: (B)

The correct choice is LED, or Light Emitting Diode, which is widely used as a visual indicator because of its efficiency, brightness, and versatility. LEDs are compact, have low power requirements, and can emit light in various colors, which makes them ideal for use in a range of applications from indicators on electronic devices to status lights and displays.

Unlike incandescent bulbs, LEDs do not produce as much heat and are much more durable, making them longer-lasting and suitable for use in situations where space and energy conservation are critical. While an LCD screen can also display information visually, it is primarily used for conveying more complex data and requires more power to operate compared to an LED indicator. A photoresistor, on the other hand, is a light-dependent resistor that changes its resistance based on light levels; it is not a direct visual indicator but rather a component that detects light levels.

Thus, LEDs stand out as the most common choice for simple visual indicators in electronic devices due to their efficiency, ease of integration, and clear visibility.