The word that best replaces the word <em>labyrinth </em>in this sentence is C) maze, because it means the same thing as a labyrinth, although other options also mean similar things.
The main reason is the purpose of the place. A maze is a network of paths and hedges that is designed as a puzzle, the objective is to find your way out. The other answers don't fulfill this objetive, although you can get lost in a jungle, for example, it is not its main purpose. A labyrinth is also designed to get lost.
Answer: Romeo describes her as light because he has new found love within her that he feels brought him out of the darkness and into a whole new world of emotions and feelings.