As a reporter or writer, which of the following opinion polls should I trust?

Question

a. a poll with a sample drawn from people who volunteer for online polls.
b. a poll where votes cast via a website, text message or 900 number.
c. a poll conducted only in urban areas that claims to represent the entire country.
d. A poll with a sample size of 500 or more that broadly represents targeted groups.

Answer 1

I'll be happy to check what YOU think.

Answer 2

I think the answer is d, but I'm not sure. Thanks.

Answer 3

I agree — d.