Passage Summary: There's a debate about whether ancient birds were cold-blooded or warm-blooded. One group points to growth rings in their bones to say they were cold-blooded, while another group points to blood vessels to say they were active and warm-blooded.

Reasoning: One study uses growth rings as evidence for cold-bloodedness, while another uses blood vessel density as evidence for warm-bloodedness.

Analysis: We have two conflicting pieces of biological evidence for the same animals. To resolve this, we need a piece of information that explains how an animal could have both growth rings (usually cold-blooded) and dense blood vessels (usually warm-blooded). Look for an answer that bridges these two biological markers, perhaps by showing that growth rings aren't exclusive to cold-blooded creatures. The goal is to find a fact that allows both studies to be 'right' about their observations but 'wrong' about their exclusive conclusions.