Which of the following can be a source of ignition in explosion risk?

The correct response highlights that electrical sparks or open flames are direct sources of ignition in contexts where explosion risks are present. In environments that contain flammable substances—such as gases, vapors, or dust—any source of ignition can lead to a fire or explosion if conditions are right. Electrical sparks can arise from faulty wiring, overloaded circuits, or the operation of equipment, while open flames from processes like welding or the operation of heaters can also ignite combustible materials.

In contrast, emotional stress, sound vibrations, and weather conditions do not serve as ignition sources. While emotional stress can impact safety awareness and decision-making, it does not physically produce a spark or flame. Sound vibrations might affect structural integrity or lead to secondary effects but are not direct ignition sources. Weather conditions can influence ignition probabilities and the spread of existing fires (such as wind aiding in rapid fire spread) but do not themselves ignite materials. Therefore, understanding the nature of ignition sources is critical in assessing and mitigating explosion hazards effectively.