Which of the following display connections has 15-pins?

RGB is a color model and signal type, not a specific connector standard with a defined pin count - analog RGB signals are carried over VGA connectors among others.

The VGA connector is a DE-15 (also called HD-15) connector with 15 pins arranged in three rows of five, carrying analog RGB video signals, horizontal sync, vertical sync, and DDC data. It was introduced by IBM in 1987 and remained a dominant display standard for decades before being replaced by digital interfaces.

DVI connectors have varying pin counts depending on type: DVI-D single link has 19 pins, DVI-D dual link has 25 pins, and DVI-I adds 4 analog pins, but none use a 15-pin configuration.

HDMI uses a 19-pin connector (Type A standard) to carry digital video and audio signals and does not use a 15-pin configuration.