Which vitamin plays a primary role in vision and the development of body cells?
a. vitamin a
b. vitamin b6
c. vitamin c
d. vitamin d

The correct answer is A) Vitamin A.

Vitamin A is a fat soluble vitamin that plays significant role in normal vision as well as development of the body cells.

Vitamin A is also called retinol because it produces a light absorbing pigment in the retina that is called rhodopsin ( formed by combining retinal and opsin). This pigment is essential for both color vision as well as vision  in the dim light ( scotopic).

This vitamin also functions as retinoic acid ( produced by oxidation of retinol) that is considered as a hormone like growth factor for epithelial and several other types of cells present in the body.

Thus, option A) is the right answer.