> the host, who knows what’s behind the doors, opens another door, say #3, which has a goat
The question, if that was indeed the formulation, very explicitly does state that the host both knows what's behind the doors, and uses that knowledge to show a goat.
Unless someone provides evidence of more ambiguity in the original question, I'm going to have to trust Marilyn's website to be quoting the question correctly... And the question seems to make the assumption very clear.
> the host, who knows what’s behind the doors, opens another door, say #3, which has a goat
The question, if that was indeed the formulation, very explicitly does state that the host both knows what's behind the doors, and uses that knowledge to show a goat.
Unless someone provides evidence of more ambiguity in the original question, I'm going to have to trust Marilyn's website to be quoting the question correctly... And the question seems to make the assumption very clear.