The person is not in room A and room B.
改否定句时be动词变否定形式,or变成and.弄不清楚全部否定还是部分否定在英语中all, both, every, everyone, everything, everybody, everywhere等与否定词not, no连用时，表示的是部分否定，而非全部否定。例如① I don’t know all of them.② I don’t like both of the books.若要表示全部否定，则应用相应得表示部分否定的否定词。例如① I know none of them.② I like neither of the books.