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?（）
- AAdd Port 21 to the TCP Ports section.
- BAdd Port 138 to the TCP Ports section.
- CAdd Port 21 to the IP Ports section.
- DAdd Port 138 to the IP Ports section.