Final answer:
The connectors commonly known as serial is RS-232.
Step-by-step explanation:
The connector commonly known as serial is RS-232. RS-232, also known as Recommended Standard 232, is a standard for serial communication that defines the signals, connectors, and protocols used for serial communication between devices.
RS-232 is often used for connecting computers to peripheral devices such as modems, printers, and serial ports. It uses a D-subminiature connector, typically with 9 pins.
On the other hand, RG-6 is a type of coaxial cable commonly used in cable television and satellite installations. RJ11 is a type of connector used for telephone connections. BNC is a type of connector commonly used for video and RF applications.
Therefore, the correct option is RS-232 for the connector commonly known as serial.