A．may not be as profitable as they are expectedB．can be……

单项选择题The author asserts that scientists ______.

单项选择题The autor wants to prove with the example of Isaac Newton that ______.

单项选择题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How could Dennis distinguish between a book and a pillow of the same size and at an equal distance in front of him A book would produce ______.

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