Question

a geologist finds four layers of sedimentary rock. she determines that no geologic events have shifted the layers. she labels the layers a, b, c, and d from the top to the bottom. which statement about these layers is accurate? a a is older than d. b b is older than c. c c is younger than a. d d is younger than d.

Explanation:

In undisturbed sedimentary rock layers, the lower layers are older. Since the layers are labeled from top - to - bottom as A, B, C, D, layer A is the top - most and layer D is the bottom - most, so A is older than D.

Answer:

A. A is older than D.