Electric washing machines, first introduced in the United States in 1925, significantly reduced the amount of time spent washing a given amount of clothes, yet the average amount of time households spent washing clothes increased after 1925. This increase is partially accounted for by the fact that many urban households had previously sent their clothes to professional laundries. But the average amount of time spent washing clothes also increased for rural households with no access to professional laundries. Which of the following, if true, most helps to explain why the time spent washing clothes increased in rural areas? ['People with access to an electric washing machine typically wore their clothes many fewer times before washing them than did people without access to electric washing machines.', 'The earliest electric washing machines required the user to spend much more time beside the machine than do modern electric washing machines.', 'In the 1920s and 1930s the proportion of rural households with electricity was smaller than the proportion of urban households with electricity.', 'People living in urban households that had previously sent their clothes to professional laundries typically owned more clothes than did people living in rural households.']