Question

The diagram below shows the layers of a rock having an ammonite:

A rock columns labeled Rock is shown. The column has three layers. The bottommost layer of the rock has one shaded circle, the middle layer has a two squares, the top layer has one star shape along with two identical organisms labeled Ammonite in the key. A key is shown at the right of the diagram. The shaded circle is marked as X, the square is marked as Y and the star is marked as Z

Which statement about the rock fossils is true?

Fossil Y is older than fossil X.
Fossil Z is younger than fossil Y.
Fossil Z existed over many periods of time.
Fossil Y existed during the same period as the ammonite.