Which of the following best describes the role of proteins and platelets in the body?

• A. They regulate body temperature
• B. They digest fats
• C. They help blood form clots
• D. They primarily transport oxygen

Answer: (C)

Proteins that act in coagulation together with platelets form clots to stop bleeding. When a blood vessel is damaged, platelets quickly stick to the injury site and release signals that attract more platelets, creating a temporary plug. At the same time, clotting proteins in the plasma trigger a cascade that converts fibrinogen into fibrin, producing a mesh that stabilizes the platelet plug into a durable clot. This coordinated action prevents further blood loss and lays the groundwork for tissue repair. The other options don’t fit because regulating body temperature is controlled by different mechanisms, fat digestion is handled by digestive enzymes, and oxygen transport is carried out mainly by hemoglobin in red blood cells.