If the distance between the worker and the ground is 300 feet or more, what must the worker do?

When the distance between a worker and the ground is 300 feet or more, it is critical to enhance safety measures due to the heightened risks associated with working at significant heights. In this context, adding an additional jumper from the cluster bar to the phase being worked is essential. This additional jumper serves as a secondary means of grounding or protection, thereby helping to mitigate the risk of electrical shock and ensure a safer working environment.

A single jumper may not provide sufficient grounding at great heights, where the potential for electrical hazards is increased. By incorporating an additional jumper, the worker creates a more robust safety system, reducing the likelihood of accidents and enhancing personal safety while performing tasks at elevated positions.

The other options, while they may seem relevant, do not directly address the specific safety requirement for working at these heights as effectively as adding an additional jumper does.