This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Which of the following is TRUE during far accommodation of the eyes? \nSelect and explain. \nA. The ciliary muscles are relaxed, B. The zonula fibers are relaxed, C. The lens is rounded, D. The focal length of the lens is sho', 'role': 'user'}, {'content': "Answer: A \nExplanation: In order to focus a distant object onto the retina (far accommodation) the lens has to decrease its refractive power, i.e., increase its focal length. This is accomplished through relaxation of the ciliary muscles that oppose the pull of the sclera. This results in a tightening of the zonula fibers and a flattening of the lens. The pupils constrict during near accommodation, perhaps to increase depth of field. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 9. Vision. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.", 'role': 'assistant'}]