Answer
a) greater height
b) I
Work Step by Step
(a) The height of the rainbow in the infrared picture will be greater than the height of the rainbow in the visible light picture. Since the top of a rainbow is red, we know that infrared light will be even higher (since infrared light has a longer wavelength).
(b) We know that the best explanation is option (I) -- that is, the height will be greater because the top of a rainbow is red and thus infrared light would be even higher.
