Mach number is significant in
A
Supersonics, as with projectiles and jet propulsion
B
Full immersion or completely enclosed flow, as with pipes, aircraft wings, nozzles etc.
C
Simultaneous motion through two fluids where there is a surface of discontinuity, gravity force, and wave making effects, as with ship's hulls
D
All of the above
Correct Answer: Supersonics, as with projectiles and jet propulsion
