问答题我们都清楚正常人每天的活动周期是大约 7～8小时的睡眠和16～17小时的清醒相互交替，我们也知道，一般来说，睡眠常在夜间进行。

单项选择题A．To sell and to inform.B．To increase prices and competition.C．To change the means of selling and buying.D．To take away chances of choosing from customers.

填空题The woman was protected in those societies by a

填空题action

单项选择题A．Mother and son.B．Father and daughter.C．Teacher and student.D．Husband and wife.