During the process of blood coagulation,vitamin-$K$ helps in the

Identify the largest agranulocytic leukocyte.

The second pregnancy of a woman terminates due to anaemia of the foetus. She has never had a blood transfusion. On the basis of this, which of the following is correct?

Give the origin of Red blood cells.

Who was the scientist to introduce $ABO$ blood groups?

$A$ 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?