The right answer is A. lens
The eye-lens is a natural convergent lens of the eye.
The eye has two natural convergent lenses: the cornea, located at the entrance of the eye, and the crystalline, biconvex lens located behind the iris and connected to the envelopes of the eye by the ciliary body. These two lenses focus the light rays on the retina, which acts as a screen in the back of the eye.