The annual survey for endorsement of a Load Line Certificate must be held within（）. ["the three month period immediately following the certificate's anniversary date","the three month period immediately preceding the certificate's anniversary date","three months either way of the certificate's anniversary date","the three month period centered on the certificate's anniversary date"]
管道动火作业前后连续（）测定混合气体中氧含量。 ["3次，每次间隔5分钟","3次，每次间隔10分钟","3次，每次间隔15分钟"]
（）是双绞线的性能指标。 ["分布电感","近端并扰","阻抗特性","光导性"]
渠道控制可以采取的方法有（）。 ["凭借强制性权利控制","利用优质服务控制","依靠品牌控制","利用辅助销售控","依靠激励手段控制"]
被译为万维网的是（）。 ["WWW","PPP","INTERNET","TCP\/IP"]
简述焦炉停止加热的故障处理？
