硫化氢检测仪的满度校验气样浓度为200ppm。
SDH传输通讯中，用于装载各种速率业务信号的信息结构是（） ["信息容器C","支路单元TU","虚拟容器VC","管理单元AU-4"]
---She has two best friends. ----（）of them is in the country. ["All","Both","No one","Neither"]
苯比水轻，密度为（）g/cm3。 ["0.679","0.779","0.879","0.979"]
与精神分裂症相比，躁狂发作不包括（） ["思维向内投","思维向外投","夸大内容及色彩之外","积极向上"]
放钢绞线时，钢绞线应（）防止触电
