—What are the elephants doing?
—They are ________. [ ]
A. walk
B. dance
C. drinking
答案:C
零阶矩()
A.MRT
B.VRT
C.MAT
D.AUMC
E.AUC
下列哪种旋转电动机的防爆结构不符合爆炸危险区域为1区的选型规定()?
A.正压型防爆结构适用于笼型感应电动机
B.增安型防爆型适用于同步电动机
C.正压型防爆结构直流电动机慎用
D.隔爆型防爆结构绕线转子感应电动机慎用