Answer: (C) Convex because it refracts the lights into a focal point.
Explanation: The natural lens in the eye is a convex lens. The lens then refracts the incoming rays and converges it into a focal point on retina to form the image. Since light diverge in all the directions from the source hence all these rays need to be focused to generate image.
The lens alters its thickness so as to focus and produce the image for the close and the far placed objects.