The author of some young adult books wants to know more about the kinds of books his readers prefer. Which of the following describes the best sampling of readers for the author to use in a survey?
A.
5,000 librarians who are registered to a national librarians’ organization
B.
5,000 customers who have just purchased ebooks from a website
C.
5,000 young adults who visit the mall on a particular day
D.
5,000 middle school students in his city