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.