You must try some of her home-made wine.It’s quite an unforgettable ______.

A．experiment

B．experience

C．effort

D．skill

燃气指令标志的含义：（）

A.电焊、检修设备操作地点等有飞溅物质的场所必须戴防护面具

B.必须戴防护面罩的场所

C.未经允许，不得摘下防护面罩