take your woodchipper, chip up guard A. point to guard b, then the woodchipper: ja or da. point to guard c, do the same. then tell them you are coming back with the woodchipper if you don’t like what you find through the door, and ask them to point to which door you should go through. pointing doesn’t require words.

edit: wait I know, don’t ask questions, just open doors, throw the guards through and see what happens. whoever survives, take that door