Native speakers perceive sentences of their own language as sequences of separate words. But this perception is an illusion. This is shown by the fact that travelers who do not know a local language hear an unintelligible, uninterrupted stream of sound, not sentences with distinct words. Which one of the following is an assumption on which the argument depends? ["Native speakers' perceptions of their own language are not more accurate than are the perceptions of persons who do not know that language.", 'Accomplished non-native speakers of a language do not perceive sentences as streams of sound.', 'It is impossible to understand sentences if they are in fact uninterrupted streams of sound.', 'People pay less close attention to the way their own language sounds than they do to the way an unfamiliar language sounds.']