Who said the following and what does it mean?

O Romeo, Romeo,
wherefore art thou Romeo?
Deny thy father and refuse thy name,
Or if thou wilt not, be but sworn my love,
And I'll no longer be a Capulet. (II. ii. 37-40)

Mercutio; he is looking for that whiny, lovesick Romeo again.
Nurse; she is trying to find Romeo so that he can spend the night with Juliet.
Juliet; she is not asking where Romeo is, but rather why he has to be a Montague.
Lady Capulet; she suspects that Juliet is in love with Romeo and will not tolerate it.