A diagnosis of respiratory failure can be made if which of t…

A diagnosis of respiratory failure can be made if which of the following are present? I. PaO2 55 mm Hg, FIO2 0.21, PB 760 mm Hg II. PaCO2 57 mm Hg, FIO2 0.21, PB 760 mm Hg III. P(A−a)O2 45 mm Hg, FIO2 1.0, PB 760 mm Hg IV. PaO2/FIO2 400, PB 750 mm Hg