承包人在知道或应该知道索赔事件发生后（）天内，提出索赔意向通知书并说明索赔事由，超过期限即丧失索赔权力。 ["27","28","29","30"]
下列关于吊顶工程中龙骨安装的要求，叙述有误的是（）。 ["边龙骨的安装应按设计要求弹线，用射钉固定","主龙骨应吊挂在吊杆上","明龙骨系列的横撑龙骨与通长龙骨搭接处的间隙不得大于1mm","次龙骨间距宜为100～300mm"]
What is the correct relative switching priority in a BLSR ring (higher to lower)?（） [" signal fail, signal degrade, manual switch"," signal degrade, signal fail, manual switch"," protection lockout, manual switch, path AIS"," forced switch, manual switch, signal degrade"," protection lockout, manual switch, forced switch"]
基站可以使用（） ["干粉灭火器","二氧化碳灭火器"]
保持阀的功用是使降压风缸内的压力一般控制在（）。 ["340～360kPa","280～340kPa","420～450kPa","340～420kPa"]
描述主要化学药剂的功用。
