Question: The Web portal AOL places opinion poll questions next to many of its news stories. Simply click your response to join the sample. One of the questions in January 2008 was "Do you plan to diet this year?" More than 30,000 people responded, with 68% saying "Yes." You can conclude that
(a) about 68% of Americans planned to diet in 2008.
(b) the poll used a convenience sample, so the results tell us little about the population of all adults.
(c) the poll uses voluntary response, so the results tell us little about the population of all adults.
(d) the sample is too small to draw any conclusion.
(e) None of these.