Which of these is a correct statement regarding the principle of superposition?
a) Every point on a wave front may be considered to behave like a point source of waves .
b) As a wave moves from one medium to another, the wave speed changes .
c) Transverse waves can be polarized, but longitudinal waves cannot .
d) The displacement of the medium at a point where waves meet is the sum of the .
e) Displacements of the individual waves .