Blood clotting in a test tube can be prevented by adding a small amount of ........

Arnold $J$. Quick is associated with the discovery or study of which vitamin?

Biological marriage of one of the following should be avoided:

Which is the appropriate pair?

Which of the following statements are correct regarding thrombocytes?
$I$ - Also known as blood platelets.
$II$ - They are cell fragments.
$III$ - Produced from megakaryocytes.
$IV$ - Their count in a normal individual ranges from $3,50,000$ to $6,00,000$ per $mm^3$.
$V$ - Involved in the process of blood coagulation.

Arrange the following formed elements in the decreasing order of their abundance in blood in humans :
$(a)$ Platelets
$(b)$ Neutrophils
$(c)$ Erythrocytes
$(d)$ Eosinophils
$(e)$ Monocytes
Choose the most appropriate answer from the options given below :