It means "where"
My translation
Juliet: Romeo, Romeo! Where are you, Romeo?
Refuse your father and your name;
Or, if you will not, but swear to my love,
And I will no longer be a Capulet.
Why would Juliet be asking who Romeo is at this point of the story?
And the other options just don't make sense. Where is the only logical answer out of all the choices