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.

Explanation: