[单选题]【阅读理解】The problem of leisure is new. Until very recent times people worked each day to the limit of their strength. Of course there were always a privileged few who had leisure; but most men had to work 12, 14, or even 16 hours a day, six days a week. As late as 1840 the average factory worker labored 72 hours a week. “Sunup to sundown” was the farmer’s day, or as another phrase puts it, “from can to can’t.”The phrase “from can to can’t” means ______. A from beginning to end B from birth to death C from morning to night D from time to time