Which of the following vitamins is mainly responsible for blood coagulation in human being?

1. A

   Vitamin K

   (a) Vitamin K. Vitamin K is required for hepatic synthesis of clotting factors II, VII, IX and X (and proteins C and S). That is the official key.

2. B

   Vitamin E

   (b) Vitamin E. Tocopherol is an antioxidant; it is not the primary coagulation vitamin.

3. C

   Vitamin A

   (c) Vitamin A. Retinol is for vision and epithelium, not clotting.

4. D

   Vitamin C

   (d) Vitamin C. Ascorbic acid is for collagen hydroxylation; scurvy bleeds from weak vessels, not from missing K-dependent factors.

Summary. Official key is (a). Vitamin K is the main coagulation vitamin in humans. E, A and C have other roles.