The two groups of organisms that share the most similar DNA based on the diagram would be turtles and frogs. This is because both turtles and frogs are classified as cold-blooded vertebrates (specifically reptiles and amphibians respectively), and within the larger classification of vertebrates, they would likely have more similar DNA compared to organisms from different major groups (like bears and salmon, or warm-blooded and cold-blooded animals).
So, the correct response is turtles and frogs.