A person standing near a grounded crane that has contacted power lines is exposed to which type of potential?

When a grounded crane comes into contact with power lines, it creates a situation where a significant difference in voltage can be present between two points. Step potential occurs when a person standing on the ground is exposed to different voltage levels across their feet, effectively creating a path for electrical current to flow through their body. This is particularly hazardous, as it can lead to severe electric shock or electrocution.

In this scenario, the person near the grounded crane could be standing on ground that has differing electrical potentials due to the current flowing through the ground from the point of contact with the power lines. If they take a step, they could bridge a high potential area with a low potential area, thus exposing them to step potential, which is specifically concerning in situations involving grounding and electrical incidents.

The other options like touch potential, ground potential, and voltage potential do not provide the same context as step potential in relation to the danger posed while standing nearby, given that step potential accounts for the voltage difference across a distance on the ground that can put someone at risk when close to such a hazardous situation.