What’s the best use for a null modem adapter?

A good item to keep in a CompTIA A+ certified technician’s toolkit is a null modem adapter. What’s a good reason to have a null modem adapter?

A) To connect two modems together without a serial port

B) To connect two computers via serial port without a modem

C) To connect a modem to a computer

D) To connect two modems and two computers together