Explanation:

Prothrombin is a plasma protein that plays a crucial role in blood clotting.

It is produced by the liver with the help of Vitamin K.

However, when bleeding occurs, blood platelets release various clotting factors, which help convert prothrombin into thrombin, an enzyme that aids in forming a clot.

Thus, blood platelets play a significant role in activating the clotting process by releasing prothrombin and other clotting factors.