Our ability to change the focus of our eyes to see objects at different distances depends on changes in the

A) frequency of impulses in the optic nerve.
B) thickness of the lens.
C) position of the retina.
D) width of the pupil.

Thickness

A measurement of an object's dimension from one side to another, indicating how wide or deep the object is.

Optic Nerve

A crucial part of the eye and visual system, transmitting visual information from the retina to the brain.

Pupil

The adjustable opening in the center of the eye through which light enters, whose size is controlled by muscles in the iris.