Final answer:
Ren's remark 'And you look so handsome tonight' is addressing someone's appearance, indicating a compliment on how a person looks for a particular occasion.
Step-by-step explanation:
When Ren remarks, "And you look so handsome tonight," it is evident that Ren is likely referring to someone's appearance. This implies that Ren is commenting on how well a person looks, which is generally related to their outfit or the way they have groomed themselves for a particular occasion. Thus, the correct answer to what Ren is likely referring to is C) Someone's appearance.