The network administrator has just finished installing a new 10/100/1000 switch, but receives reports from the server administrator that servers connected to the new switch seem to be experiencing slow LAN connections. The network administrator checks the port connecting the new switch to the core switch and sees the following information:

Which of the following is the MOST likely cause of the slow connections?（）

A. The servers have not had VLAN tagging enabled on their NICs.
B. Speed and duplex have not been set.
C. VLAN tagging was not set on the trunk.
D. The servers have been connected with CAT5 cable.