What must be used to access areas not designed for passenger contact?

The correct answer emphasizes that tools are essential for accessing areas that are not designed for passenger contact, such as inside the machinery space or electrical compartments. These areas typically require manipulation for maintenance or inspection, and tools provide the necessary means to open panels, access equipment, and perform tasks safely and effectively.

When considering the other options, access panels, while certainly important for gaining entry to certain areas, still require tools to be properly opened or removed. Keys can be essential for secured areas that require unlocking, but they do not inherently facilitate access to the actual components inside these areas. Safety gloves are important for protecting the hands and promoting safety while working, but they do not assist in the actual act of gaining access. Thus, tools remain the vital means for conducting necessary work in these restricted areas.