Has he never been to Oxford before?
Where has he never been before?
Who has never been to Oxford before?
Has he never been to Oxford or Cambridge before?
He has never been to Oxford before, has he?
Has Nick taken my umbrella by mistake?
What has Nick taken by mistake?
Who has taken my umbrella by mistake?
Has Nick taken my umbrella or my gloves by mistake?
Nick has taken my umbrella by mistake, hasn't he?