6. Read the following excerpt from the story.
Until this day, how well the house had kept its peace. How carefully it had inquired, 'Who goes there? What's the password?" and, getting no answer from the only foxes and whining cats, it had shut up its windows and drawn shades in an old-maidenly preoccupation with self-protection which bordered on a mechanical paranoia.
It quivered at each sound, the house did. If a sparrow brushed a window, the shade snapped up. The bird, startled, flew off! No, not even a bird must touch the house!
Which of the following devices is most prominent in the above excerpt?