Which term describes the United Kingdom's process of returning the delegation of authority from the central government back to the regional governments of Scotland, Wales, and Northern Ireland?

A. devaluation

B. coalition

C. federation

D. devolution

"Devolution" would be the term that describes the United Kingdom’s process of returning the delegation of authority from the central government back to the regional governments of Scotland, Wales, and Northern Ireland, since this involves transferring power back to a lower level.