布袋除尘器主要由（）、（）、（）构成。
参考答案：箱体、布袋、清灰设备及反吹设备
A．1∶3
B．3∶1
C．5∶1
D．1∶1
A．( What are the differences between marketing and cost-effective publicity
B．( Could you say something on the subject of cost-effective publicity
C．( How much will the conference on marketing and sales cost us
D．( When will the subject of the 50-minute conference be publicized
