Which of the following is considered a distress signal?

Answer: C — dye marker

A dye marker is a recognized distress signal, particularly when used in maritime situations. It can create a bright-colored cloud or pattern in the water, which is highly visible and helps rescuers locate individuals in distress. The use of a dye marker is effective as it provides a visual signal that can be seen from a distance, especially from the air, enhancing the chances of a timely rescue. In contrast, while a flag with a cross might signify a signal, it may not be universally recognized as a distress signal in maritime contexts. A single whistle blast typically serves as a warning or signaling method rather than a distress signal, which generally requires a repetitive sound. A bright flashlight, although useful for signaling, does not qualify as an official distress signal without specific patterns or purposes outlined by maritime regulations.