馈电开关发生短路时,应()。
A.更换开关
B.查找原因
C.检查灭弧罩和触头
D.查找故障
参考答案:C
主动脉瓣关闭不全()。
A.局限在心尖部
B.向剑突处传导
C.向颈部传导
D.向心尖部传导
E.向左腋下传导
Chinese and Maths ______ my favourite lessons. [ ]
A. all are
B. both are
C. are all
D. are both