Light is registered in the retina when photons hit molecules of the pigment rhodopsin and change the molecules' shape. Even when they have not been struck by photons of light, rhodopsin molecules sometimes change shape because of normal molecular motion, thereby introducing error into the visual system. The amount of this molecular motion is directly proportional to the temperature of the retina. Which one of the following conclusions is most strongly supported by the information above? ['Molecules of rhodopsin are the only pigment molecules that occur naturally in the retina.', 'The visual systems of animals whose body temperature matches that of their surroundings are more error-prone in hot surroundings than in cold ones.', 'As the temperature of the retina rises, rhodopsin molecules react more slowly to being struck by photons.', "The temperature of an animal's retina depends on the amount of light the retina is absorbing."]