Answer:
D. in the same direction as they are moving
Explanation:
There are two types of waves as follows:
1. LONGITUDINAL WAVE:
Such types of waves, in which particles of the medium vibrate along the direction of propagation are called ‘Longitudinal Waves’. For example; sound waves, and waves produced in spring. Longitudinal waves consist of compressions and rare fractions.
2. TRANSVERSE WAVE:
Such waves in which particles of the medium execute perpendicular motion to the direction of propagation, are called ‘Transverse Waves’. For example; waves produced in water, light waves, and radio waves. Transverse waves consist of Crests and Troughs.
Therefore, the correct answer is:
D. in the same direction as they are moving
