The correct answer is option 2: Calcium. Calcium is the element involved in blood clotting. When an injury occurs, a series of complex chemical reactions take place to form a blood clot, a process known as coagulation. Calcium plays a crucial role in this process by activating various proteins and enzymes that promote clot formation. Without sufficient calcium, blood would not be able to clot properly, leading to excessive bleeding and difficulty in wound healing. It is important to note that while calcium is necessary for blood clotting, an imbalance or deficiency in calcium can also lead to abnormal clotting or increased risk of blood clots.