In the summer of 1936 a polling service telephoned 10,000 United States voters and asked how they planned to vote in the coming presidential election. The survey sample included a variety of respondents—rural and urban, male and female, from every state. The poll predicted that Alfred Landon would soundly defeat Franklin Roosevelt. Nevertheless, Roosevelt won in a landslide.
Which one of the following, if true, best explains why the poll’s prediction was inaccurate?
(A) The interviewers did not reveal their own political affiliation to the respondents.
(B) Only people who would be qualified to vote by election time were interviewed, so the survey sample was not representative of the overall United States population.
(C) The survey sample was representative only of people who could afford telephones at a time when phone ownership was less common than it is today.
(D) No effort was made to determine the respondents’ political affiliations.
(E) Because the poll asked only for respondents’ candidate preference, it collected no information concerning their reasons for favoring Landon or Roosevelt.
How to choose between B and C.? Please advice.