Prothrombin is a

Match the columns:

Column-$I$ (Blood group)	Column-$II$ (Antigen present)
$A$. $A$	$p$. $B$
$B$. $B$	$q$. $A$
$C$. $AB$	$r$. $A$ and $B$
$D$. $O$	$s$. $A, B$ and $O$
	$t$. $NIL$

Assertion $(A)$: Blood coagulates in uninjured blood vessels.
Reason $(R)$: Uninjured blood vessels release an anticoagulant heparin.

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.

Which statement is correct for $WBC$?

Which mineral element is responsible for the blood clotting process?