The $pH$ of blood is

Mature erythrocytes are enucleated in the following animals $EXCEPT$:
i. Rat
ii. Monkey
iii. Llama
iv. Camel
v. Elephant
Choose the correct answer from the options given below.

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 $O$
	$t$. $NIL$

Leucocytes $(WBCs)$ are considered as true cells because

Match the Column $I$ (blood corpuscles) and Column $II$ (stem cells/precursors from which they are formed).

Column $I$ (Blood corpuscles)	Column $II$ (Stem cells/precursors)
$i$. Thrombocytes	$a$. Lymphoid stem cells
$ii$. Granulocytes	$b$. Megakaryocytes
$iii$. Erythrocytes	$c$. Myeloid stem cells
$iv$. Agranulocytes	$d$. Reticulocytes

Choose the correct option given below.

Four children belonging to the same parents have the following blood groups $A$,$B$,$AB$ and $O$. Hence,the genotypes of the two parents are: