Which of the following would be most useful in determining how modern-day lions, tigers, and domestic cats are related? Measuring the heights of adult males and females of each species. Analyzing differences in the population size of each species. Comparing amino acid sequences of a specific protein from each species. Finding fossils from each species at a certain location.

The correct answer is:<br /><br />**Comparing amino acid sequences of a specific protein from each species.**<br /><br />### Explanation:<br />To determine how modern-day lions, tigers, and domestic cats are related, scientists would look at genetic or molecular evidence, such as comparing amino acid sequences of a specific protein. This approach provides insights into evolutionary relationships by identifying similarities and differences in the genetic code that have accumulated over time. <br /><br />- **Measuring heights**: Physical traits like height can vary due to environmental factors and do not necessarily reflect evolutionary relationships.<br />- **Analyzing population size**: Population size is influenced by ecological and environmental factors, not evolutionary lineage.<br />- **Finding fossils**: Fossils provide historical context but may not directly link modern species without additional molecular evidence.<br /><br />Molecular data, such as amino acid sequences, is one of the most reliable tools for determining evolutionary relationships among species.