Final answer:
Fossil records, such as the Archaeopteryx, support the theory of evolution by providing evidence that modern species share a common ancestor and showing the changes in organisms over time.
Step-by-step explanation:
The piece of evidence that supports the theory of evolution is a) Fossil records. Among fossil discoveries, the Archaeopteryx is a significant find, showcasing characteristics of both reptiles and birds, suggesting that modern species share a common ancestor. Furthermore, fossils provide us with concrete evidence that past organisms differ from today's species and demonstrate evolutionary progressions. Interestingly, the study of fossils was the primary source of evidence for evolution until recent times, showing how organisms have changed and adapted to their environments over time.