How will a wave change as it moves from a layer of higher velocity into a lower layer of lower velocity?

Explanation:

Wave is defined as a disturbance or oscillation that travels through space-time, accompanied by a transfer of energy. Wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium.

The velocity of wave is equal to the product of its wavelength and frequency (number of vibrations per second). Longitudinal waves like sound waves travel through a medium.

Therefore, a wave move from a layer of high velocity to that of a lower velocity the wavelength changes (that is, decreases) as it moves.

real, smaller and upside-down.   so the answer should be b.

the part of the wave he is travelling on is the crest