How could Dennis distinguish between a small ball and a large ball from a distance of 3 feet The large ball would produce ______.

单项选择题If someone holds a book 6 feet directly in front of Denis and then moves it only 1 foot directly in front of him, what change in sound does. Dennis hear

单项选择题The writer says that a blind baby is doubly handicapped in comparison to a sighted child because ______.