Here's the fourth sneak peek to the episode 7x12 in which Cristina has to deal with her slow-witted resident while being under Chief's wing.
Episode synopsis : Arizona seeks Mark's advice as she tries to reconcile with Callie, who has big news of her own; Teddy must make a key decision for Henry during his surgery; and on the same day the residents receive a new crop of interns, the Chief announces he is looking for a new Chief Resident.
