A 2012 Gallup Survey Interviewed by Phone a Random Sample

A 2012 Gallup survey interviewed by phone a random sample of 474,195 U.S. adults. Participants were asked to describe their work status and to report their height and weight (to determine obesity based on a body mass index greater than 30) . Gallup found 24.9% obese individuals among those interviewed who were employed (full-time or part-time by choice) , compared with 28.6% obese individuals among those interviewed who were unemployed and looking for work.
What is the population?

A) All U.S. adults
B) All U.S. adults who are obese
C) All U.S. adults who read Gallup surveys
D) The 474,195 U.S.adults interviewed