双滚筒采煤机一般有电动机、截割部、牵引部及附属装置组成。
参考答案：对
伴有消化性溃疡病、左心室肥厚及阵发性室上性心律失常的高血压患者，宜使用（）
A.吗啡
B.利血平
C.尼莫地平
D.维拉帕米
E.硝苯地平
The genetic engineering, ______ progress has been very rapid recently, is perhaps the most important of all the sciences．
A．to which
B．with which
C．in which
D．for
