Lobe-finned fishes were present in the oceans of the world approximately 400 million years ago. The first tetrapods (vertebrates that had limbs and could move on land) date to about 365 million years ago. One hypothesis states that early tetrapods evolved from lobe-finned fishes. Which of the following is the best plan for testing the hypothesis?

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DNA sequence is typically the best gauge for evolutionary relationships. However, the size itself is irrelevant. We would need to compare the sequences.

The next best thing would be the arrangement of bone structures, since bone structure is slow to evolve. Similar internal structures imply relationship.

Choosing fish from different geographical locations would tell us nothing about the tetrapods.

Using radioactive dating gives us the time period each organism lived in, but does not give any evidence for evolutionary relationships.