According to Arizona regulations, county officers must be?

In Arizona, county officers are required to be elected residents of the respective counties they serve. This requirement ensures that the individuals in positions of authority are not only representative of the local populace but also accountable to their constituents. Elected officials are expected to understand the unique needs, challenges, and perspectives of their community, as they are directly chosen by the voters. This system promotes democratic governance and local participation in decision-making processes.

The other options, such as being appointed experts or selected by neighboring counties, do not align with the principles of local governance and representation that are central to the structure of county offices in Arizona. Independent hiring would also undermine the accountability of county officials to the residents, as it removes the element of direct electoral choice that is integral to public service positions at the county level.