A user is unable to connect to the network. A network technician is able to determine that there is a problem on the switch. All other users on that switch are able to connect successfully to the network. Which of the following is a probable cause？（）

A.Switching loop is occurring on the switch.
B.Wrong subnet mask on the switch.
C.Incorrect SNMP settings on the switch.
D.Port is misconfigured on the switch.