Ageologist finds ripples preserved in ancient sedimentary rock that look just like ripples made by water in mud. he concludes that there was once water in that location that created the ripples.

why is this conclusion reasonable?
a.
because water and mud behaved very differently in the past than they do today

b.
because sedimentary rock always forms under water

c.
because sedimentary rock never forms from mud

d.
because water and mud behaved in a similar way in the past as they do today