Some people who have a deficiencey of vitamin A exhibit symptoms of night ... ...

Some people who have a deficiencey of vitamin A exhibit symptoms of night blindness. This condition allows normal sight during the day (in bright light) but virtual blindness when it becomes dark, when people without the condition could at least make out shapes and outlines. It is likely that this deficiency is causing its effects by:
(A) blocking the passage of information down the optic nerve to the brain.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in 14. The Nervous and Endocrine Systems