The basic language of modems and dial-up remote access systems is:

A.
Asynchronous Communication.

B.
Synchronous Communication.

C.
Asynchronous Interaction.

D.
Synchronous Interaction.

Explanation:
Asynchronous start-stop is the physical layer used to connect computers to modems for many dial-up Internet
access applications, using a data link framing protocol.
Incorrect Answers:
B: Dial-up modems use Asynchronous, not synchronous, communication.
C: Dial-up modems connect to a remote system using communication, not interaction.
D: Dial-up modems connect to a remote system using communication, not interaction.

https://en.wikipedia.org/wiki/Asynchronous_serial_communication