Both asexually and sexually
The correct answer to this question is this one: they lacked oxygen. The earliest organisms were completely heterotrophic in nature because of the reason that they lacked oxygen. <span>A heterotroph is an organism that cannot fix carbon and uses organic carbon for growth. </span>
<span>the platelets in the blood comes in contact with air they decompose to form thermoplastic, thermoplastic combine with inactive thrombotic, formed by the combination of Vitamin K and Calcium ions,to form active thrombi,thrombi combines with the fibrin in the blood plasma to form Fibrin, this Fibrin entangle with blood corpuscles and thus clot is formed... i hope i helped
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