An optional unified county is organized under Public Act 139 of 1973, the Optional Unified Form of Government Act, in which a county board of commissioners must share executive functions with either an appointed county manager (Unified form, Alternative A) or an elected county executive (Unified form, Alternative B). The difference between these two alternative forms is that a county manager serves at the pleasure of the board, while a county executive is an elected official who serves fixed, four-year terms. In both forms, the county manager or executive can veto resolutions and budget line items passed by the board of commissioners. Public Act 139 also requires any county reorganizing as a unified county the creation of particular boards, commissions, authorities, and elective offices, while it requires the abolition of others in the county. The optional unified option of organization grants more powers to the administrative structure of the county, but provides for less flexibility than either general law or charter counties.