Identify the following sample designs:
a. The names of 200 patrons of a casino are drawn from a list of visitors for the past month, and a questionnaire is administered to them.
b. A radio talk show host invites listeners to call in and vote yes or no on whether handguns should be banned.
c. A dog food manufacturer wants to test a new dog food. It decides to select 100 dog owners who feed their dogs semimoist canned food, 100 who feed their dogs dry food, and 100 who feed their dogs food.
d. A poll surveys men who play golf to predict the outcome of a presidential election.