In 936, a U. S. magazine agency conducted a poll on the presidential election through telephone interviews and interviews with car owners found in car registration data. More than 2 million tests were recovered from more than 10 million test papers issued by it. Looking at it, most people support the Republican presidential candidate, Langdon, and do not like another presidential candidate, Roosevelt, but in the end, Roosevelt was elected. Which of the following reasons best describes the failure of the magazine's test? ['U. S. voters are fickle.', 'Not enough test people.', 'Test volume recovery is not high.', 'Test subjects as people who have a phone and a car mainly belonged to the middle and upper social classes in the United States at the time, and they did not account for the majority of voters.']