Which vitamin is primarily responsible for blood clotting?

Vitamin K plays a crucial role in blood clotting, which is essential for preventing excessive bleeding when injuries occur. It is a fat-soluble vitamin that is primarily involved in the synthesis of certain proteins required for blood coagulation, including prothrombin, one of the key clotting factors. Without sufficient vitamin K, the blood-clotting process is impaired, leading to a higher risk of uncontrolled bleeding.

In contrast to vitamin K, other vitamins listed do not have a direct role in blood clotting. Vitamin A is important for vision, immune function, and skin health. Vitamin B12 is essential for red blood cell formation and neurological function, while vitamin C is crucial for collagen synthesis and acts as an antioxidant, but neither contributes directly to the blood clotting mechanism. Thus, the unique role of vitamin K in facilitating the complex process of coagulation underscores why it is the correct answer to the question regarding blood clotting.