The correct answer to this question is D, Molex. These connectors have 4-pins. They are used to attach DC power to a PC cabinet's drives. Along with being a type of connector, Molex is also a manufacturer. Since the 1940s, Molex manufactured plugs and sockets. They are not the only manufacturer to make these connectors.
However, they were one of the first to do so. Them being one of the first has allowed their name to stick. The connector in the image provided is a smaller one. It is mainly used for floppy drives. There is another type of Molex connector, which is larger and used for CDs and DVD drives.