二战期间，德国入侵苏联的作战计划的代号为（）A、台风 B、海狮 C、霸王 D、巴巴罗

挡脚板应固定在脚手架外立杆外侧，密目式安全立网里侧。( )

I'm interested in _____ you have said. [ ]

A. all that

B. all what

C. that

D. which

They stayed with me three weeks,______ they drank all the wine I had.     [    ]

A. which                                   

B. which time    

C. during which time                        

D. during which

简单邮件传送协议SMTP使用的端口号为( )

A．20

B．21

C．23

D．25

手拉倒链使用前应做.等项目检查（）

A.外观检查，各部分有无变形和损坏

B.上.下空载试验，检查链子是否缠扭，传动部分是否灵活

C.手拉链条有无滑链和掉链现象

D.超载实验