Read the following citation, and then answer the question.
United States. Cong. Senate. Committee on Entertainment and Music Resources. Hearing on the Impact of Jazz. 110th Cong., 1st sess. Washington: GPO, 2008.
In this citation, “GPO” is
A. the name of the government.
B. the organization responsible for the research.
C. the agency that created the document.
D. the publisher of the document.