After Reading the Paragraph Below, Answer the Question(s) That Follow(s)

After reading the paragraph below, answer the question(s) that follow(s) .
Walter has noticed that, as he has gotten older, his peripheral nervous system has been in decline. For example, his visual abilities have declined markedly-in particular his night vision is poor. Also, his ability to perceive tastes is much less active than in his youth.
-Walter's poor night vision is caused by

A) age effects on cone cells.
B) age effects on rod cells.
C) age effects on the cornea.
D) age effects on the iris.