The scene was a plain, bare, monotonous vault of a school-room, and the speaker's square forefinger emphasized his observations by underscoring every sentence with a line on the schoolmaster's sleeve. The emphasis was helped by the speaker's square wall of a forehead, which had his eyebrows for its base, while his eyes found commodious cellarage in two dark caves, overshadowed by the wall. The emphasis was helped by the speaker's mouth, which was wide, thin, and hard set. The emphasis was helped by the speaker's voice, which was inflexible, dry, and dictatorial. What metaphor does the author use to describe the speaker's forehead and eyes? A) A wall and a cave B) A line and a sleeve C) A vault and a square D) Fir trees and pie crust