现场井控关井原则为“发现溢流立即关井，疑似溢流关井检查”。（）
参考答案：对
David ________ from the analysis of the traffic accident that it had been caused by human error.[ ]
A. announced
B. acknowledged
C. concluded
D. considered
椎-基底动脉系统短暂性脑缺血发作最常见的临床表现为（）
A.眩晕、恶心和呕吐
B.耳鸣和耳聋
C.跌倒发作
D.吞咽困难
E.复视
