Correct option is B
In compressible fluid flow, when a gas undergoes supersonic flow and encounters an obstruction or sudden change in area or pressure conditions, it may experience rapid, nearly discontinuous changes in fluid properties.
This abrupt transition zone is called a:
Shock Wave
It is a thin region (typically a few microns thick) across which:
Pressure increases suddenly
Temperature increases
Velocity decreases (often from supersonic to subsonic)
Density increases
Entropy increases → irreversible process
These sharp changes happen almost instantaneously, leading to non-isentropic, high-gradient phenomena.
