Answer:
Fossil Z is younger than Fossil Y.
Explanation:
For any age-related questions in geology, we have to consider the basic principle of stratigraphy. According to which, sediment layers on top harbor younger fossils whereas <u>layers</u> on the <u>bottom</u> have <u>older fossils</u>. In the case given here, Fossil Z is younger because it is in the top layer and Fossil Y is in the middle layer. The other two options are completely wrong because Fossil Y cannot be older than Fossi X and likewise, Fossil Z doesn't exist in multiple periods rather it is present only once.
