The plot for the pressure ratio along the length of the convergent divergent nozzle is shown in the given figure. The sequence of the flow conditions labeled (1), (2), (3) and (4) in the figure is respectively
(a) Supersonic, sonic, subsonic and supersonic
(b) Sonic, supersonic, subsonic and supersonic
(c) Subsonic, supersonic, sonic and subsonic
(d) Subsonic, sonic, supersonic and subsonic.