(c) There is sudden change in pressure, temperature and density
For shock wave Mach number is greater than one i.e., velocity of source is greater than velocity of sound. In this case the pressure and velocity at an arbitary point of the stream can be influenced only by disturbance acting at point that lie on or inside the zone of action (or Mach cone) so option (a) is wrong.
When shock occur then there is sudden change in pressure a temperature and density. As flow is changing from supersonic to subsonic, so velocity and pressure and temperature will change. Only stagnation enthalpy and temperature may remain constant. But static value definitely change.
