Among the following vitamins the one whose deficiency causes rickets (bone deficiency) is :

Rickets is a disease that affects bone development, especially in children, leading to soft and weak bones. This condition is caused by a deficiency in certain vitamins. Let us recall the roles of the vitamins given in the options:

Vitamin A is important for vision, immune function, and skin health. Its deficiency causes night blindness and other eye problems, but not rickets.

Vitamin B is actually a group of vitamins (like B1, B2, B6, B12). They help in energy production, nerve function, and red blood cell formation. Deficiency can cause anemia, beriberi, or other issues, but not rickets.

Vitamin D helps the body absorb calcium and phosphorus from food, which are essential minerals for building strong bones. Without enough vitamin D, bones become soft and weak. In children, this deficiency specifically causes rickets.

Vitamin C is crucial for the immune system, wound healing, and collagen production. Its deficiency leads to scurvy, characterized by bleeding gums and fatigue, but not rickets.

Therefore, the vitamin whose deficiency causes rickets is vitamin D.

Hence, the correct answer is Option C.