原油密闭输送管道中进站压力超高保护系统的保护顺序是什么？
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请说明喷气发动机与活塞式发动机相比，他的优点在哪里？
Which two of these are characteristics of multicast routing？ （）
A. multicast routing uses RPF
B. multicast routing is connectionless.
C. In multicast routing， the source of a packet is known.
D. When network topologies change， multicast distribution trees are not rebuilt， but use the originalpath
E. Multicast routing is much like unicast routing， with the only difference being that it has a a groupof receivers rather than just one destinatio
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