Which status indicates that a unit requires additional resources or training?

The choice indicating that a unit requires additional resources or training is recognized by the designation A-4. This status specifically communicates that a unit is not fully mission-capable and faces needs that must be addressed to improve its functional capabilities. When a unit is assigned an A-4 status, it underscores the urgency for support in areas like personnel, equipment, and essential training to achieve operational readiness.

In contrast, the other options represent different levels of readiness or capability. The A-1 designation typically denotes a unit that is fully mission-capable, while A-Level is not a specific status but rather refers to a classification that may encompass various readiness levels. METL (Mission Essential Task List) pertains to the critical tasks a unit must accomplish, and while it informs about training priorities, it does not specify a need for additional resources or training on its own. This distinction makes A-4 the correct answer in identifying a unit's requirement for enhancements to its operational effectiveness.