The correct answer is C. Dreary.
This is because Le Morte d'Arthur is full of melancholy inducing moments due to the fact that everything will fall apart at a certain point. Arthur's death, and his loss, is inevitable, so is the fall of Camelot, and of his Knights of the Round Table.
"to" because too is when there's too much of something
Colloquial yet solemn as the characters portrayed a specific sector of society in an era while approaching it in an emotional aspect of it by giving the main character more of a sensitive character compared to the others
I'm pretty sure it would be A. She might be a secretive girl who everyone believes is an open-book.