Which enzyme is responsible for the conversion of inactive fibrinogens to fibrins?

In case of disputed parentage,the blood group analysis of the mother,child,and alleged father can:

$A$ man whose blood group is not known meets with a serious accident and needs blood transfusion immediately. Which one of the blood groups readily available in the hospital will be safe for transfusion?

Blood examination of an anemic person reveals large,immature,nucleated erythrocytes without hemoglobin. Which of the following,if added to their diet,would alleviate the symptoms?

Which of the following substances,if introduced into the blood stream,would cause coagulation of blood at the site of its introduction?

Identify the cells and their functions based on the provided figure:
$(a)$ Fig. $A$ - Megakaryocyte - formation of platelets
$(b)$ Fig. $B$ - Lymphocyte - synthesis of antibodies
$(c)$ Fig. $A$ - Eosinophil - secrete antihistamine
$(d)$ Fig. $A$ - Neutrophil - secrete heparin