Which of the following could be used as a signaling device in distress?

Using smoke as a signaling device in distress is effective because it creates a visible and distinctive signal that can be seen from a distance, especially in open spaces or over water. The presence of smoke can indicate a location in emergencies, and the color of the smoke can be used to convey different messages; for instance, colored smoke can stand out against natural backgrounds, making it more easily noticed by rescuers.

This method is sometimes used in conjunction with a fire or a flare, where generating a significant amount of smoke can increase visibility. Smoke signals are particularly advantageous during the day when they can be seen from the air, enhancing search and rescue operations.

In contrast, while lanterns, candles, and mirrors all have their purposes, they may not be as effective in creating large visible signals or can be situationally limited by weather conditions, visibility range, or the need for specific handling. For example, lanterns and candles provide light but may not be visible over long distances unless carefully positioned or maintained. Mirrors can signal by reflecting sunlight but require precise angles and conditions to be effective in catching attention. Thus, smoke stands out as a robust and reliable option in a distress scenario.