In which of the following situations must you report to the National Response Center?

Reporting to the National Response Center (NRC) is primarily required in situations that pose a significant threat to public safety or the environment. The correct choice highlights the necessity of reporting when the general public is evacuated for over one hour. This is crucial because such evacuations indicate a serious incident that could have widespread implications for health and safety.

When the public is forced to evacuate, it implies that there has been a significant hazard, potentially involving hazardous materials, which could endanger lives. This type of situation necessitates immediate reporting to the NRC so that appropriate response measures can be coordinated at a national level, ensuring that resources and support are made available promptly.

The other options cover important incidents but do not reach the threshold that requires immediate federal reporting. For example, a non-fatal injury, property damage over $30,000, or the detection of toxic gases can indicate serious situations, but they do not always necessitate evacuation or the same level of urgency in reporting to the NRC. Thus, those scenarios would typically be handled at the state or local level before considering a national response.