A pharmacy wants to survey its customers to find out which brand of toothpaste they prefer. Which survey methods are likely to be biased?
Choose all answers that are correct.


A.
A survey is sent to the customers who are on the pharmacy’s frequent buyer list.

B.
One hundred people from the pharmacy’s customer list are selected at random, called on the phone, and asked.


C.
Those customers who buy toothpaste with a coupon are selected, and the toothpaste brand they purchased is recorded.

D.
Every 10th customer who enters the pharmacy on 1 day is selected and asked.