Which vitamin deficiency is most likely to cause night blindness?

Night blindness, or nyctalopia, is primarily associated with a deficiency of vitamin A. This vitamin plays a crucial role in the maintenance of healthy vision, particularly in low-light conditions. Vitamin A is essential for the synthesis of rhodopsin, a light-sensitive pigment found in the rods of the retina, which is vital for seeing in dim light. Insufficient levels of vitamin A can impair the regeneration of rhodopsin, leading to difficulty seeing at night.

In contrast, deficiencies of vitamin B12, C, and D do not specifically cause night blindness. Vitamin B12 is primarily important for red blood cell formation and neurological function. Vitamin C is a powerful antioxidant that plays roles in collagen synthesis and immune function but does not directly impact vision. Vitamin D is primarily involved in calcium absorption and bone health and is not related to the mechanisms of night vision. Therefore, vitamin A deficiency is clearly the correct answer regarding its direct impact on night blindness.