"you" is an understood subject most often in IMPERATIVE sentences. these are commands, like, "go to your room" or "have a seat."
in those sentences, the subject is "(you) go to your room" or "(you) have a seat."
in the answer choices: mr. burghart is the subject in choice A. "we" is the subject in choice B. "looks" is the subject in choice D.
C has the understood you: (you) please have another glass of orange juice. because it's a command, it's assumed that you're addressing a certain person (you).
