What type of signaling equipment must be kept in the operating compartment of locomotives and cabooses?

The correct choice highlights the essential signaling equipment that must be available in the operating compartment of locomotives and cabooses, which are critical for safety and communication on the railways. Fusees are emergency signaling devices used to provide a visible warning in case of a malfunction or emergency situation. The red flag serves as a flagging device to signal train movements or halt. A white light is used in various circumstances to signal safety and alertness, particularly in low visibility conditions.

Together, these items ensure that crew members can effectively communicate in both routine operations and emergency situations. They provide visual signals that can be recognized from a distance, which is crucial in preventing accidents and ensuring safe train operations. Proper signaling equipment is fundamental to maintaining operational safety and preparedness.

In contrast, the other options contain items that may not be standard or universally required for the operational safety of locomotives and cabooses, which can diminish their relevance in this context.