On a Linux device, which of the following commands will start the Nessus client in the background so that the Nessus server can be configured?

'nessus +' is not a valid Linux shell syntax or a recognized Nessus command-line flag and would result in an error.

'nessus *s' is not valid syntax; the asterisk is a shell glob wildcard and does not serve as a background or flag operator.

The '&' shell operator in Linux/Unix instructs the shell to fork the process and run it in the background, returning control to the terminal immediately. Running 'nessus &' starts the Nessus client as a background process so that the administrator can then interact with the shell to configure the Nessus server without waiting for the client process to exit.

'nessus -d' is not the standard flag for backgrounding a process; flags like -d typically indicate debug or daemon mode depending on the application, not shell backgrounding.