A geologist is studying a geologic cross section of rock layers in a national park. The rock layers appear to be well preserved and undisturbed. Which statement best identifies the oldest rock layer in the cross section?

The oldest rock layer is the top layer of the cross section.
The oldest rock layer is the top layer of the cross section.

The oldest rock layer is above the bottom layer of the cross section.
The oldest rock layer is above the bottom layer of the cross section.

The oldest rock layer is the bottom layer of the cross section.
The oldest rock layer is the bottom layer of the cross section.

The oldest rock layer is above the middle layer of the cross section.