Concept:The embryos of vertebrates provide evidence of the order in which animal groups evolved over time.
Explanation:The early embryos of different vertebrates look very similar.
This similarity shows that they share a common ancestor.
The groups appeared in this evolutionary order: fishes, amphibians, reptiles, birds, and mammals.
Fishes evolved first, so they are the oldest among the vertebrate groups shown.
The animal labelled I represents the fish.
This means that animal I is the oldest creature in evolutionary history in the diagram.
Answer:C. i
