Apharmacy wants to survey its customers to find out which brand of toothpaste they prefer. which survey methods are likely to be biased? select each correct answer.
a: a survey is sent to the customers who are on the pharmacy’s frequent buyer list. b: those customers who buy toothpaste with a coupon are selected, and the toothpaste brand they purchased is recorded. c: one hundred people from the pharmacy’s customer list are selected at random, called on the phone, and asked. d: every 10th customer who enters the pharmacy on 1 day is selected and asked.