Q. Consider the following:
1. Fibrin
2. Thrombin
3. Thromboplastin
4. Calcium ions
Which among the above are required in normal blood clotting?

• (A) Only 1 & 2
• (B) Only 1, 2 & 3
• (C) Only 1, 2 & 4
• (D) 1, 2, 3 & 4