Night blindness is a classic manifestation deficiency of:

The question asks about the deficiency that causes night blindness.

• Night blindness, also known as nyctalopia, is a condition where vision is impaired in low light.
• Vitamin A (retinol) is a fat-soluble vitamin essential for good vision, particularly in dim light. It is a crucial component of rhodopsin, a light-sensitive pigment found in the rod cells of the retina.

A deficiency in Vitamin A leads to an insufficient amount of rhodopsin, impairing the eye's ability to adapt to darkness, thus causing night blindness.

Night blindness is a classic manifestation of a deficiency of Vitamin A.

$\text{Vitamin A}$