Question: What type of protocol is used for transferring CDR files between a CGF and the BD over the Bx reference point?
Option 1: HTTP
Option 2: Diameter
Option 3: FTP or FTAM
Option 4: SSH
Explanation: The correct answer is Option 3 because, according to the provided text, a common standard file transfer protocol such as FTP (File Transfer Protocol) or FTAM (File Transfer and Access Management) is used for transferring CDR files between a CGF and the BD over the Bx reference point.