Select the example that represents self-selected sampling.
A) Aaron asks a couple of questions whenever he thinks a customer seems interested as they walk by his store.
B) Aaron conducts a survey by selecting every fifth customer who enters his store.
C) Aaron randomly approaches customers throughout the day to ask them questions about their shopping preferences.
D) Aaron invites a group of customers who have previously participated in his store's loyalty program to take part in a focus group discussion.