单项选择题
A．Cara Lang, a Fortunate Girl B．Take Our Daughters to Work Day C．Children’s Day and Work Day D．Ms. Foundation, an Organization for Women
A．Getting off to work with a minimum effort helps save one’s energy. B．Dr. Kleitman explains why people reach their peak at different hours of day. C．Habit helps a person adapt to his own energy cycle. D．Children have energy cycles, too.