Which of the following is required for safely assembling a mobile crane?

Clear communication with ground personnel is essential for safely assembling a mobile crane. Effective communication ensures that all team members are aware of the operations taking place, potential hazards, and necessary safety protocols. It allows for coordination between the crane operator and ground personnel, which is crucial for monitoring the surrounding area, guiding the crane's movements, and providing assistance as needed without creating confusion or increasing risk.

While multiple operators may be beneficial depending on the complexity of the lift, they are not strictly necessary for the assembly process itself. A safety harness is important during crane operation, particularly for personnel working at height, but this pertains more to preventing falls rather than the assembly of the crane itself. Having a first aid kit on site is a good safety practice, but it does not directly relate to the specific requirements of safely assembling a mobile crane. Thus, clear communication stands out as a critical component in ensuring safety during this process.