<P><STRONG><FONT size=4>A network addministrator wants to control which user hosts can access the network based on their MAC address . What will prevent workstations with unauthorized MAC address from connecting to network through a switch?<BR> <BR> A.BPDU<BR> B.Port security<BR> C.RSTP<BR> D.STP<BR> E.VTP<BR> F.Blocking mode<BR> </FONT></STRONG></P><P><STRONG><FONT size=4>完全看不懂????题目是什么意思!!!</FONT></STRONG></P><P><STRONG><FONT size=4></FONT></STRONG> </P>