The correct answer is option 4, Vitamin K. Vitamin K is a fat-soluble vitamin that plays a crucial role in blood clotting. When a blood vessel is injured, a series of chemical reactions occur to form a clot to prevent excessive bleeding. Vitamin K is necessary for the production of certain proteins called clotting factors, which are involved in this process. These proteins help to activate a protein called fibrinogen, which then forms fibrin threads that create a mesh to capture blood cells and form a clot.

Option 1, Vitamin A, is not involved in blood clotting but is important for vision, immune function, and cell growth.

Option 2, Vitamin D, is important for the absorption of calcium and phosphorus, which are essential for bone health and other bodily functions, but it does not play a role in blood clotting.

Option 3, Vitamin E, is an antioxidant and helps to protect cells from damage. It is not directly involved in blood clotting.

Therefore, the correct answer is Vitamin K.