A _____ can be used to exchange written messages by telephone, though this method is outdated and rarely used.

• A. Email
• B. Chat App
• C. FAX
• D. Teletypewriter (TTY or TDD)

Answer: (D)

Exchanging written messages over a telephone line is the key idea here. A teletypewriter, or TTY/TDD, was built specifically to send typed text through a standard phone line, letting people communicate by keyboard with the other end either displaying or printing the text. It’s a purpose-built solution for text over telephone networks, which is why it best fits the description, even though it’s now largely outdated.

Email and chat apps rely on internet connectivity, not a traditional phone line. A fax also uses phone lines, but it transmits full page images of documents rather than ongoing typed messages in a conversational form, so it’s not the best fit for “exchanging written messages by telephone.”