Deficiency of Vitamin A causes [C] Night blindness. Vitamin A is crucial for maintaining healthy vision, particularly in low-light conditions. Its deficiency can lead to reduced ability to see in dim light, eventually progressing to night blindness. This occurs because Vitamin A is necessary for the synthesis of rhodopsin, a pigment in the retina that enables vision in low-light environments. Hair fall [A], dysentery [B], and weakness [D] are not typically associated with Vitamin A deficiency, although it can contribute to weakened immunity and overall health if severe and prolonged.