Answer:
A). A line graph from the National Oceanic and Atmospheric Administration showing average summer temperatures in the Southwest United States from 2001–2015.
Step-by-step explanation:
As per the given details, the most significant source that would assist Evan in his research would be a 'line graph issued by the National Oceanic and Geographic Administration which display standard temperatures during the summer season in the SouthernWest part of the United States among the years 2001-15.' This would assist him in analyzing the warming trends in that part for the last fifteen years and make reliable conclusions. Thus, option A is the correct answer.