电气火灾事故的常见原因包括( )。
A.设备缺陷、安装不当
B.电气设备过热
C.电火花、电弧
D.电气设备操作不当
参考答案:A,B,C
已知命题p:|m+1|≤2成立.命题q:方程x2-2mx+1=0有实数根.若¬P为假命题,p∧q为假命题,求实数m的取值范围.
Sometimes the expert ________ a task from a historical point of view.
A.doesn’t need to approach
B.dare settle
C.needs not to solve
D.dare not to deal with