A remote user cannot connect to the office via VPN. The user has established Internet connectivity. Which of the following is the MOST likely next step in troubleshooting?（）

• A、Power cycle the VPN concentrator at the office.
• B、Determine if the VPN service is running at the office.
• C、Reinstall the VPN client at the remote computer.
• D、Determine if the user has the correct VPN address and password.