What is the source of wave drag exerted on the supersonic airfoil?

A)
Skin friction
B)
Trailing vortex
C)
Shock waves
D)
Viscous boundary layer

Correct Answer :   Shock waves


Explanation : Wave drag is a result of pressure distribution which is exerted over the airfoil. This is a consequence of formation of shock waves and expansion wave pattern due to the presence of supersonic flow.