Which of the following is an acceptable reason for a hospital to divert an ALS unit?

Choosing to divert an Advanced Life Support (ALS) unit due to an internal disaster is a valid decision that prioritizes patient safety and hospital operations. An internal disaster could include various emergencies, such as a fire, flooding, or hazardous materials incident that compromises the hospital's ability to adequately care for patients. In such situations, diverting incoming units allows the hospital to manage the crisis effectively and ensure that resources are available for patients already receiving care.

While other factors like staff shortages or workers' action might also necessitate diverting ALS units, they typically do not meet the same level of urgency or immediate threat to patient safety as an internal disaster would. A non-operable MRI, for instance, would not typically influence the decision to divert ambulances, as it does not directly impact the hospital’s ability to provide critical emergency services.