Explanation:

Correct option 2: platelets

Blood clots are formed due to the presence of certain cells in the blood called platelets (also known as thrombocytes). These cells play a crucial role in the clotting process by sticking to the site of injury, forming a temporary "platelet plug," and releasing substances that help in the formation of fibrin, a protein that stabilizes the clot. Additionally, fibrin produced from fibrinogen (a plasma protein) forms a mesh-like structure that solidifies the clot.