User A at Company A is trying to transfer files to Company B, using FTP. User A can connect to the FTP server at Company

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User A at Company A is trying to transfer files to Company B, using FTP. User A can connect to the FTP server at Company B correctly, but User A cannot get a directory listing or upload files.
The session hangs.
What are two possible causes for this problem? (Choose two.)

A. Active FTP is being used, and the firewall at Company A is not allowing the returning data connection to be initiated from the FTP server at Company B.
B. Passive FTP is being used, and the firewall at Company A is not allowing the returning data connection to be initiated from the FTP server at Company B.
C. At Company A, active FTP is being used with a non-application aware firewall applying NAT to the source address of User A only.
D. The FTP server administrator at Company B has disallowed User A from accessing files on that server.
E. Passive FTP is being used, and the firewall at Company B is not allowing connections through to port 20 on the FTP server.