For the experiment that Haley, Sarah, and Becky are conducting, a bar graph would be the most appropriate way to display their data.
In this scenario, they are testing different types of materials (wool, cotton, and nylon) as insulators by measuring the temperature of the water in each sock over time. The bar graph can effectively show the temperature of the water at various time intervals for each type of sock material side by side, making it easy to compare the effectiveness of each material as an insulator.
A line graph could work if they wanted to show the temperature change over time, but multiple lines would complicate the comparison between materials. A pie graph is not suitable here because it does not represent changes over time or different categories of data. A scatter plot is typically used for showing relationships between two continuous variables and is not appropriate in this case.
Therefore, the best choice is a bar graph.