Questions: Blood coagulation is a process that requires clotting factors, platelets and vitamin - calcium; K calcium; D sodium; B potassium; C

The answer is the first one: calcium; K.

Explanation for each option:

1. calcium; K: This is the correct answer. Blood coagulation requires calcium ions (Ca²⁺) and vitamin K. Calcium is essential for various steps in the coagulation cascade, and vitamin K is necessary for the synthesis of certain clotting factors in the liver.

2. calcium; D: This is incorrect. While calcium is indeed required for blood coagulation, vitamin D is not directly involved in the coagulation process. Vitamin D primarily helps in calcium absorption and bone health.

3. sodium; B: This is incorrect. Sodium is not a key player in the blood coagulation process, and vitamin B is not directly involved in coagulation. Vitamin B complex is more related to energy metabolism and red blood cell formation.

4. potassium; C: This is incorrect. Potassium is not involved in the coagulation process, and vitamin C is more related to collagen synthesis and immune function rather than blood clotting.

Summary: Blood coagulation is a process that requires calcium ions and vitamin K. Calcium is crucial for the activation of various clotting factors, and vitamin K is necessary for the synthesis of these factors.