Answer:
unbelieving
Explanation:
incredulous means unwilling or unable to believe something.
Wallace places emphasis on the word "adjust" because he is addressing our realities and way of thinking as "default." He expresses the importance of paying attention to your surroundings, and adjusting to other perspectives and ways of thinking. He compares our ignored experiences to the water fish swim in but were never taught to notice.
Montag gets on the subway and starts reading the Bible, because he wants to memorize some lines from it. However, he is being constantly distracted and interrupted by an advertisement for Denham's Dentrifice toothpaste, as its jingle is played over and over again on the subway. He gets really mad because of it and starts screaming and yelling, before he leaves at the next stop.