更换新电刷最好能按原型号、规格更换，若用其他型号代替时，要求其性能与原电刷性能尽可能地相近。
参考答案：对
—What’s that terrible noise over there?
—The workers ______ the boxes from the back of the truck.
A．have carried
B．are carrying
C．carry
D．will carry
职能型结构
