(B) "On average, people who lived a century ago had considerably less leisure time than we do today." The passage concludes that, because people who lived a century ago had fewer diversions to amuse themselves, they likely read more than we do today. However, this is assuming that people who lived a century ago had a similar amount of free time to what we have today but just spent it differently. Yet, if people a century ago worked longer days and had less leisure time than we do, as (B) states is the case, they may not have been able to read more. This weakens the argument.
(C) "The number of books sold today is larger than it was a century ago." This answer choice is incorrect because the number of books sold does not necessarily tell us who reads more. Perhaps most books read a century ago were borrowed rather than sold. Perhaps people who buy books today are unlikely to read them. Perhaps the population change is responsible for the difference in the number of books sold. The point here is that the number of books sold does not affect the argument.
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