动车组列车只发售二等坐车学生票，学生票为全价票的80％。（）
参考答案：错
Part of the family________out on holiday. They are supposed to be back at the end of this month. [ ]
A .is
B. are
C. was
D. were
直方图是描述统计分布的惟一形式。（）
