RJ11 is the standard interface for telephone lines and is required for faxing functionality. Most multifunction devices (MFDs) that support faxing need to be connected to a phone line via an RJ11 connection to transmit and receive faxes. B . RJ45 is used for Ethernet connections, not for faxing. C . USB is used for connecting peripherals but does not support faxing. D . Bluetooth is a wireless technology, not typically used for fax functionality. Reference: CompTIA A+ Certification Study Guide Official CompTIA IT Fundamentals (ITF+) Study Materials