The best answer is C) Character, although Characterization may be a better word for what the sentence does.
The sentence helps give you a better idea of who Simon Levant is. This sentence does not establish the theme, or drive the plot, or establish conflict (unless his mustache has grown tired of this treatment and is plotting against him). The sentence helps to form the character of the detective, to give life to him and establish an image of himself in the mind of the reader.
