What can foreign objects like rocks or loose hardware cause during ground operations?

Foreign objects such as rocks or loose hardware can lead to accidents and damage during ground operations primarily because they pose a significant safety hazard. When an aircraft is in motion on the ground, any foreign object in its path can cause physical damage to the aircraft itself or can lead to accidents involving other vehicles, personnel, or equipment.

For instance, if a loose piece of hardware is present on the taxiway, it can be sucked into the aircraft's engine or can damage the landing gear, leading to serious consequences during takeoff or landing. Furthermore, these objects can create hazardous conditions for ground personnel who may be working in the vicinity, potentially causing tripping hazards or injuries.

While engine overheating, fuel leaks, and mechanical failures can occur for various reasons, including maintenance issues or design flaws, these scenarios are not directly linked to the presence of foreign objects during ground operations. Instead, the immediate impact of such objects is tangible in terms of accidents and physical damage to the aircraft or surrounding environment, solidifying the choice as the correct answer.