When we reached the station the train had not arrived yet；so we_______．

太阳系的行星绕太阳运动时，其机械能守恒，动量矩不守恒。（ ）

单项选择题太阳系的行星绕太阳运动时，其机械能守恒，动量矩不守恒。（ ）

Progress so far has been very good. , we are sure that ...

单项选择题Progress so far has been very good. , we are sure that the project will be completed on time.

生产成本明细账和管理费用明细账的格式宜采用多栏式。           （     ）A．正确 B．错误

不定项选择生产成本明细账和管理费用明细账的格式宜采用多栏式。           （     ）