To Assess Racial Discrimination in the Labor Market, a Researcher

To assess racial discrimination in the labor market, a researcher sends resumes to help-wanted ads in the newspaper. She assigns Black-sounding names to half of the résumés and white-sounding names to the other half; then she records whether each job applicant was called back for an interview. This is an example of

A) an experiment.
B) a survey.
C) field research.
D) the use of existing data.