Which of the following forms blood clots?

when there is an injury, the platelets in the blood comes in contact with air they decompose to form thromboplastin, thromboplastin combine with inactive prothrombin, formed by the combination of Vitamin K and Calcium ions, to form active thrombin, thrombin combines with the fibrinogen in the blodd plasma to form Fibrin, this Fibrin entangle with blood corpuscles making the clot form

Therefore your answer would be Fibrin.

I hope this helped better than others!

the correct answer is 4) heat and pressure

metamorphic rocks arise from transformation of existing rocks types, in a process called metamorphism. during metamorphism the original rock(prolith) change into metamorphic rock by heating (150-200c) and pressure of more than 1000 bar. the original rock can be sedimentary, igneous, or existing metamorphic rock.