Grouping the united states into the northeast region, the northwest region, the southeast region, and the southwest region would be departmentalization by

Grouping the united states into various regions would be departmentalization  by location.
Various organizations and entities use the departmentalization based on task, function or service etc. A divide which is based on various locations will be called departmentalization by location as it involves northeast, northwest, southeast and southwest locations.

a. would be the answer : )

explanation:

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