Answer 1

A transverse wave consists of crests and troughs.
The elevation or hump in a transverse wave is called crest. It is that part of the transverse wave in which all the medium particles are above the line of zero disturbance of the medium.
The depression or hollow in a transverse wave is called trough. It is that part of the transverse wave in which all the medium particles are below the line of zero disturbance of medium.