标准工单分类错误的是（）？
A.日常维修标准工单
B.非维修领料工单
C.大修标准工单
D.安装回撤标准工单
参考答案：B
The fire, believed to due to illegal construction on the building’s roof, was brought under control after an hour.
A．have occurred
B．occur
C．have been occurring
D．be occurring
一度房室传导阻滞（）
A.提前出现的QRS波群，宽大畸形
B.P波与QRS波群无关
C.PR间期逐渐延长，继之QRS波群脱落，呈周期性
D.PR间期固定，有时QRS波群脱落
E.PR间期延长
