Which of the following prevents the conversion of prothrombin to thrombin in an undamaged blood vessel?

$A$ 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?

Match the following:

Column-$I$	Column-$II$
$(1)$ Neutrophil	$(a)$ Inflammation
$(2)$ Eosinophil	$(b)$ $6-8\%$
$(3)$ Basophil	$(c)$ Phagocytes
$(4)$ Monocytes	$(d)$ Resists infections

When the blood of one person is mixed with the serum of another person,in certain cases,clumping of $RBCs$ takes place. This clumping is due to:

Examination of blood of a person suspected of having anaemia shows large,immature,nucleated erythrocytes without haemoglobin. Supplementing his diet with which of the following is likely to alleviate his symptoms?

What happens when calcium is removed from freshly collected blood?