The correct option is C Dispersion
The principle of superposition of waves is used to find the resultant displacement, which is used in interference and diffraction to find the change at edges.
Stationary waves are obtained by reflection of a wave at a solid surface. The resultant amplitude can be found out using superposition principle.
Dispersion of waves is a phenomenon which depends on nature of matter and hence superposition can't be used to find resultant displacement.