Ben's Grandfather Has Not Been Able to Read Ben a Bedtime

Ben's grandfather has not been able to read Ben a bedtime story for quite some time now. Grandpa says his eyes are just getting tired very early in the evening but Ben knows that his grandfather is unable to focus on reading because the lens in his eyes have become unable to focus the words directly onto the retina. His grandfather's lens are:

A) too thick, so the image is focused too near the lens
B) too thin, so the image is focused too near the lens
C) too thin, so the image is focused too far from the lens
D) too thick, so the image is focused too far from the lens