国产缝纫机的型号编制中J、G、F分别代表什么缝纫机的代号？
参考答案：
J表示家用缝纫机；G表示工业用缝纫机；F表示服务性行业缝纫机。
--- We expected you yesterday．
--- I'm sorry, I you to say that I couldn't be here until today．
A．must have called
B．would be calling
C．could have been calling
D．should have called
一辆东风牌汽车对地面的压强大约为1.8×105Pa，表示的物理含义是：______．
