Latisha is a Linux administrator. She is remotely accessing a Linux server at a location without high$-$speed Internet over an Integrated Services Digital Network $($ISDN$)$ connection. This is still fast enough for her to perform command$-$line administration. What manages her login to the remote server?

Question $3$ options:

Auth$0$

Public switched telephone network $($PSTN$)$

Remote Authentication Dial In User Service $($RADIUS$)$

Single sign$-$on $($SSO$)$