Answer:
Personally from my own perspective the meaning of this quote is how some people put on a mask to make other people happy and or so other people don't notice how sad/empty they feel.
Explanation:
I believe it's unknown since the Mississippi is the predicate and unknown is a describing word, a.k.a. an adjective but I'm not sure
Good luck, hope I helped!
Protagonist. A protagonist is the leading character of a story, therefore that’s your answer.