In computer networking a multicast address is an identifier for a group of hosts that have joined amulticast group. Multicast addressing can be used in the Link Layer （OSI Layer 2）， such as Ethernet Multicast， as well as at the Internet Layer （OSI Layer 3） as IPv4 or IPv6 Multicast. Whichtwo descriptions are correct regarding multicast addressing？（） ["The first 23 bits of the multicast MAC address are 0x01-00-5E. This is a reserved value thatindicates a multicast application","The last 3 bytes （24 bits） of the multicast MAC address are 0x01-00-5E. This is a reservedvalue that indicates a multicast application","To calculate the Layer 2 multicast address， the host maps the last 23 bits of the IP address intothe last 24 bits of the MAC address. The high-order bit is set to 0","The first 3 bytes （24 bits） of the multicast MAC address are 0x01-00-5E. This is a reservedvalue that indicates a multicast applicatio"]
起重机主要结构件腐蚀深度达原厚度的（）时，则应予报废。 ["15％","10％","7％"]
安全边际量=实际销售量一（）。
事故停机中导水叶剪断销剪断，为什么制动后不允许撤出制动？
下列说法正确的是（） ["高雷诺数下容易转捩是因为惯性力大，扰动大","马赫数是惯性力与粘性力之比","层流和紊流的判断依据的是上临界雷诺数","雷诺输运方程和随体导数是完全等价的"]
分批法的成本计算期是（）的。
