Option 1: Thrombin. Thrombin is a protein enzyme that plays a crucial role in the blood clotting process. When there is an injury or damage to a blood vessel, thrombin is produced to trigger the clotting cascade. It converts fibrinogen, a soluble protein in the blood, into insoluble fibrin strands, which form a mesh-like network that traps platelets and other blood cells to form a blood clot. This clot helps to prevent excessive bleeding and promotes wound healing.

Option 2: Haemoglobin. Haemoglobin is a protein found in red blood cells that carries oxygen to the body`s tissues. It does not cause blood clotting; its primary function is oxygen transport.

Option 3: Pectin. Pectin is a soluble fiber found in fruits and is often used as a gelling agent in food preparation. It has no direct role in blood clotting.

Therefore, the correct answer is option 1 - Thrombin.