What type of switch is prohibited from being fed from more than a single circuit unless marked as a multi-circuit switch?

The correct response indicates that a multiple snap switch must be explicitly marked as a multi-circuit switch if it is to be fed from more than a single circuit. This is crucial for safety and code compliance, as a typical snap switch is designed and expected to handle the load from one circuit only. If multiple circuits are connected without proper marking, it may lead to confusion during maintenance and could create overload conditions, posing a fire hazard.

The implication here is that proper labeling helps ensure that anyone working on the electrical system can identify the switch's intended use and limitations, thereby preventing improper connections that could endanger life or property. This adherence to regulations is essential for maintaining safe electrical practices.