CompTIA A+ 220-901

Answer: C - A modem is required for communication of POTS, or Plain-Old Telephone System.

Key Takeaway - A modem changes digital signals to analogue signals (and vice-versa) so computers can communicate over the Plain-Old Telephone System, which is also referred to as the Public Switched Telephone Network. An Ethernet NIC, or Network Interface Card, allows communication over an Ethernet Network, while a WAP provides wireless access to client computers.