Rick spoke about Shelly's departure as if she was already gone. Which revision changes the underlined verb to the subjunctive mood? Change was to were. Change was to had been. Change was to is. Change was to was not.

The revision that changes the underlined verb to the subjunctive mood is the first one - change was to were.

Rick spoke about Shelly's departure as is she were already gone.

If you use the subjunctive mood here, you will add the possibility that she is not gone yet, which is something the indicative mood cannot show to the same extent.