D. because water and mud behaved in a similar way in the past as they do today
One of the fundamental theories in the field of earth science is the theory of uniformitarianism.
Uniformitarianism was proposed by James Hutton in the 18th century in Scotland. The theory states that “geologic processes occurring today have occurred in times past and that the present is the key to past”.
The simple meaning of the theory is that, the processes on earth today such as weathering, erosion, e.t.c have also occurred in times past. Those processes still occur today and an understanding of such events today will help us have a better insight into the past.
Therefore, ripple marks just as they form today from action of mud and water would be formed in a similar way in the past.