In isentropic flow of a perfect gas (a) the velocity always decreases in conduits of increasing area. (b) the velocity is always critical at the throat of a nozzle. (c) if the flow is subsonic flow...

In isentropic flow of a perfect gas

(a) the velocity always decreases in conduits of increasing area.

(b) the velocity is always critical at the throat of a nozzle.

(c) if the flow is subsonic flow through a convergent nozzle, the maximum velocity is always at the throat.

(d) if the flow is in a convergent-divergent nozzle, the maximum velocity is always at the throat.