A Sociologist Studying Freshmen at a Major University Carried Out

A sociologist studying freshmen at a major university carried out a survey, asking (among other questions) how often students went out per week, how many hours they studied per day, and how many hours they slept at night. The sociologist used an introductory sociology class to carry out the survey. The population of interest is:

A) the students at the university.
B) the students in the sociology class.
C) the freshmen at the university.
D) the freshmen in the sociology class.