719、检修动火前,必须( )煤气设施内可燃气体,并用可燃气体测定仪测定合格或爆发实验合格后方可动火

719、检修动火前,必须( )煤气设施内可燃气体,并用可燃气体测定仪测定合格或爆发实验合格后方可动火

A.置换

B.放空

C.点燃

正确答案是A