Answer:
The correct answer is D. A cataract is an opacity of the crystalline lens or its covering.
Step-by-step explanation:
Cataract is the partial or total opacity of the lens. The opacity causes the light to disperse inside the eye and cannot focus on the retina, creating diffuse images, the most common cause of blindness treatable with surgery. It has various causes but is mostly attributed to age although there are also many other causes. Over time particles of a brown-yellow color are deposited that gradually turn the lens opaque.