$(a)$ What are fossils?
$(b)$ Explain the importance of fossils in evolutionary relationships.

(N/A) Fossils are the preserved remains,impressions,or traces of organisms that lived in the past,found within sedimentary rock layers.
$(b)$ Fossils provide direct evidence of evolution by showing the existence of organisms that lived millions of years ago but are now extinct. They help in establishing evolutionary relationships by revealing the transition between different groups of organisms (connecting links) and demonstrating how modern species evolved from more primitive ancestral forms over geological time.