Which of the following scenarios illustrates subliminal stimulation?

Which of the following scenarios illustrates subliminal stimulation?
 
  A) Caleb who initially found his classroom too bright eventually became accustomed to the brightness.
  B) While driving down a highway, Deborah perceived the objects outside to be moving faster than her car.
  C) In a restaurant, several mirrors were arranged in such a way that the restaurant appeared to be large and spacious despite it being small.
  D) In an experiment, an audio track was played at such a low volume that the participants were not aware of it.