Which statement is true about the Call Admission Control （CAC） feature in VoIP networks？（） [" CAC is used to allocate enough bandwidth for the number of calls that are allowed on the VoIP network."," CAC is used to protect the quality of the voice calls by preventing call establishment if enough resources are not available on the network."," CAC provides queuing mechanisms for voice calls if the packets exceed the configured or budgeted rate."," In a VoIP network the CAC can be replaced with the LLQ QoS mechanism if it has been properly implemented."]
加气混凝土是含（）材料加水并加适量的发气剂和其他外加剂，经混合搅拌，经蒸压养护制成。 ["硅","锰","砂","水泥","尾矿粉"]
在行业竞争中，处于主导地位的企业采取垄断各种可行的技术专利的做法，这属（）战略。 ["进攻","维持","袭击","收获"]
干粉灭火系统按照系统结构特点分为（）。 ["储气瓶型干粉灭火系统","储压型干粉灭火系统","管网干粉灭火系统","预制干粉灭火系统","干粉炮灭火系统"]
检测抗HCV最常用的检测方法是（） ["酶联免疫吸附试验","间接免疫荧光试验","重组免疫印迹试验","放射免疫试验","间接血凝免疫试验"]
属于电气安全用具和一般防护用具有哪些？
