During the propagation of a plane progressive mechanical wave,
(a) all the particles are vibrating in the same phase.
(b) the amplitude of all the particles is equal.
(c) the particles of the medium execute SHM.
(d) the wave velocity depends upon the nature of the medium.
Choose the correct alternatives:
1. (a, b, d)
2. (a, c)
3. (b, c, d)
4. (c, d)