阴极发光的原理是（）。
参考答案：通过电子束轰击样品使之发光以研究其成分晶体形态及二者相互之间的关系等特征
供婴幼儿食用的零售包装配方奶粉
10BaseT is an Ethernet LAN tem meaning a maximum transfer rate of 10 Mbps that uses baseband signaling and twisted pair cabling. A 10BaseT Ethernet LAN has a ______ topology.
A．star
B．ring
C．bus
D．none of the above
