IP multicasting is a set of technologies that enable efficient delivery of data to manylocations on a network．Rather than making multiple copies of a message intended to bedistributed to multiple recipients at the (71) of origin of a message，multicasting initiallysends just one (72) and does not copy it to the individual recipients until it reaches theclosest common point on the network，thereby (73) the bandwidth consumed．Networkperformance is significantly (74) because it isn’t bogged down with the processing andtransmission of several large data files；each receiving computer doesn’t have to (75) thetransmitting server for the file．
A．loop
B．find
C．search
D．query
参考答案：D
解析：IP多播是允许同时给网络上很多主机提供数据的一种技术。它并不是每次复制很多副本去发送给每一个在这个IP多播组中的接收者，而是最初只发送单一信息，并没有立即复制信息去发给每个接收者，而是直到到达网络中最近的一个共通点时才开始复制，从而最大限度地减少了对带宽的消耗。它使得网络的性能明显得到改善，一是因为它没有立即处理和传输几个大型数据文件；二是接收端计算机不需要查询该传输服务的