SINUMERIk820S 系统是指（）控制系统，专为经济型数控机床设计的。
参考答案：步进电动机
Do you know().
A．who writing is she to
B．who he is writing to
C．she is writing to whom
D．who is she writing to
国际收支是国民经济总体指标之一，它反映一国与他国之间商品、劳务等全部交易状况。( )
