Denise is researching the impact of gentrification, an increase in middle-class and affluent homeowners, on the population of her high school. Which two sources would be most useful to her research?

state assessment results for the last ten years for Denise’s high school
a research article with data showing changes in the student population at Denise’s school
an opinion piece in the local newspaper from a parent about new school zone policies
interviews with local realtors about the changes to neighborhoods near Denise’s school