世界上最早使用麻醉剂的是我国古代的()。A.扁鹊 B.华佗 C.张仲景 D.孙思邈

干式过滤器是基于筛除效应、深层效应和静电效应原理来清除气体中的固体杂质的。

David failed in the final examination last term and only then________how much time he had wasted

before.[ ]

A. had he realized  

B. he had realized  

C. did he realize

D. he realized

患儿，6个月，因腹泻、呕吐频繁、烦渴、多饮入院。查体：体温40℃，皮肤干，前囟凹陷，肌张力高。

诊断最可能为( )

A．中度高渗性脱水

B．重度高渗性脱水

C．中度低渗性脱水

D．重度低渗性脱水

E．以上均不对

人工基坑开挖安全距离要求？