The diagram below shows different layers of sedimentary rocks.

picture showing seven layers of rocks of different colors labeled a, b, c, d, e, f, and g from top to bottom; a and b are parallel horizontal layers at the top of the diagram and c, d, e, f, and g are slanted layers with c closest to the surface and g at the bottom.

based on the diagram, which of these inferences is most likely correct?

a. layer a is older than layer b.
b. layer c is older than layer e.
c. layer f is younger than layer d.
d. layer b is younger than layer g.