Which Is a Possible Explanation for the Failure of Scientific

Which is a possible explanation for the failure of scientific sampling method in the 1948 U.S.election when Dewey was solidly predicted to defeat Truman?

A) The error was in assuming that respondents who said they were decided would wind up voting in the same ratio as those who had already undecided.
B) The error was in assuming that respondents who said they were undecided would wind up voting in the same ratio as those who had already decided.
C) The error was in assuming that non-respondents would wind up voting in the same ratio as those who had already decided.
D) The error was in assuming that Democrats who said they were undecided would wind up voting in the same ratio as those Republicans who had already decided.