What is the significance of the glass of milk, apple, and pear in the third section?
Actually, this is one of those nice instances in which the author pretty much spells out what he means. By that I mean, Bradbury has Montag long that the world gives him some sign that it approves of him, that it accepts him. The milk, apple, and pear would be those things. They are quiet and domestic, which are two things this new world (and Montag's life) are not, and they would be signs of the world approving of him.