Practice question

Correct option is B, Circular muscles. In Sensory System Eye Physiology, the accurate description is Circular muscles, and that is what you should commit to memory. Keep the definition tight and the role clear — cause and effect line up with Circular muscles — that is the mechanism or reason the stem is pointing to. Then Circular muscles is the answer you can defend. Check yourself by covering the options and writing the answer first, then matching the letter — that builds confidence. If the wording feels dense, translate it into everyday language first, then map that plain sentence back onto Circular muscles.