Which of the following is a common cause of electric shock?

Wet surfaces are a common cause of electric shock due to their ability to conduct electricity more effectively than dry surfaces. When surfaces are wet, particularly with water that contains impurities (such as mineral content), they allow electrical currents to flow more easily. This increases the risk of accidental contact with live electrical components, which can result in an electric shock to a person touching the wet surface.

High humidity can also contribute to electric shock risks, as it may increase the likelihood of moisture on surfaces, but it is not as directly impactful as wet surfaces themselves. On the other hand, dry conditions actually reduce the risk of electric shock since dry materials typically do not conduct electricity well. Proper grounding is a safety measure that prevents electric shocks by providing a low-resistance path for current to flow safely to the ground, yet it is not a cause of electric shock itself.

Thus, wet surfaces present a clear and significant risk for electric shock due to their conductive properties.