单项选择题
To which of these does IP multicast send packets？（）
A. a single host B. a subset of hosts C. all hosts sequentially D. all hosts simultaneously
单项选择题 Whichoftheseportsdoessyslogusetosendmessagestoasyslogserver？（）
单项选择题 WhichoftheseisabenefitofESM？（）
单项选择题 WhichoftheseisaLayer2transportarchitecturethatprovidespacket-basedtransmission optimizedfordatabasedonadual（counter-rotating）ringtopology？（）
