Which of the following is a main function of platelets?

Platelets, also known as thrombocytes, primarily function in the process of hemostasis, which is the cessation of bleeding. When a blood vessel is injured, platelets quickly adhere to the site of injury and begin to aggregate (clump together). This aggregation forms a temporary "platelet plug," which serves as an initial barrier that prevents further blood loss. Additionally, platelets release chemical signals that facilitate the coagulation cascade, ultimately leading to the formation of a stable blood clot that strengthens the initial plug and seals the wound.

The other options describe functions not associated with platelets. Regulating body temperature is primarily the role of the hypothalamus and is controlled through various physiological mechanisms. Carrying oxygen is the main function of red blood cells, which contain hemoglobin that binds to oxygen in the lungs and transports it to tissues. Transporting nutrients is mainly the responsibility of the plasma component of blood and specialized cells, not platelets.