ANS:B - serial

COM port means Communication port and not Component Object Model, It refers to the serial port interface on IBM PC-compatible computers. It might refer not only to physical ports, but also to virtual ports, such as ports created by Bluetooth or USB-to-serial adapters. COM ports are traditionally hardware Serial ports. Which were generally used for Keyboard & mouse.

"The Microsoft MS-DOS and Windows environments refer to serial ports as COM ports: COM1, COM2, . Etc. ".