1. Which kind of evidence did scientists use to determine that some animals moved back to a marine life after first evolving as land mammals? a. The fossil record
b. Comparison of homologous structures
c. DNA evidence
d. All of the above

Instead of gathering evidence from a single field, the pair pulled together research from many disciplines, including paleontology, molecular biology and conservation ecology, to give a far larger picture of what was happening when animals transitioned from the land to the sea across millennia.

Explanation:

it's probably D. all of the above because scientists use all of these examples

but im not 100% sure

the fossil record provides evidence of a common ancestor to many species.