Rheumatoid arthritis is a/an ......... disease.

Primary lymphoid organs $- P$
Secondary lymphoid organs $- Q$
$I -$ Appendix, $II -$ Peyer's patches of small intestine,
$III -$ Thymus, $IV -$ Spleen, $V -$ Lymph node, $VI -$ Bone marrow, $VII -$ Tonsils
Select the correct option for $P$ and $Q$.
$\quad P \quad \quad Q$

Which cells are responsible for the production of antibodies?

Match the type of immunity listed in Column-$I$ with the examples listed in Column-$II$. Choose the answer that gives the correct combination of alphabets of the two columns:

Column-$I$ (Types of immunity)	Column-$II$ (Example)
$A$. Natural active	$p$. Immunity developed by heredity
$B$. Artificial passive	$q$. From mother to foetus through placenta
$C$. Artificial active	$r$. Injection of antiserum to travellers
$D$. Natural passive	$s$. Fighting infections naturally
	$t$. Induced by vaccination

Which immunoglobulin is present in abundant amounts in the mother's initial milk secretion (colostrum)?

In the given figure,what does the part labeled '$A$' represent?