Which of the Following Is the Most Common Cause of Blindness

Which of the following is the most common cause of blindness in older persons?

A) The retina of a 60-year-old person allows in only a third as much light as a 20-year-old person.
B) The optic nerve becomes less efficient in transmitting nerve impulses to the brain.
C) The lens of the eye becomes less transparent.
D) The portion of the retina with the highest acuity thins and degenerates.