发票封面设计主要是用来管理发票，宣传相关规定有利于发票（）便于统计而设置的。
A.上交
B.保存
C.交易
D.审计
参考答案：D
We all feel puzzled why the students _____ the same mistakes repeatedly in exams.
A．were making
B．have been making
C．had made
D．will be making
化妆品定义是什么？
