The command-line interface tells a user that it's ready to receive commands by displaying a specific set of characters called a(n)
a) commandb) promptc) signald) key

B) prompt

Explanation:

Prompt tells a user that it's ready to receive commands by displaying a specific set of characters.

For example in windows it can be:

C:\Temp>, The prompt states that user is currently in C drive Temp directory.

in Linux based operating systems it can be:

[email protected]:~/Documents$

where it is in the format [email protected]:~directory$