To focus its eyes, an octopus does not change the shape of its lens, as is the case in humans. Instead, an octopus moves its rigid lens back and forth, as in a camera. This changes the distance from the lens to the retina and brings an object into focus.
(a) If an object moves closer to an octopus, must the octopus move its lens closer to or farther from its retina to keep the object in focus?
(b) Choose the best explanation from among the following:
I. The lens must move closer to the retina-that is, farther away from the object-to compensate for the object moving closer to the eye.
II. When the object moves closer to the eye, the image produced by the lens will be farther behind the lens; therefore, the lens must move farther from the retina.