You configure you Windows 2000 Professional computer for Internet connection Sharing and for TCP/IP filtering as shown in the exhibit.(Click the Exhibit button.) You test your TCP/IP filtering configuration from another client computer. You can access Web sites, but you cannot access FTP sites.   What should you do to be able to access FTP sites?（）

• A、Add Port 21 to the TCP Ports section.
• B、Add Port 138 to the TCP Ports section.
• C、Add Port 21 to the IP Ports section.
• D、Add Port 138 to the IP Ports section.