The term 'active immunity' means

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 $Q$.
$\quad P \quad \quad Q$

Assertion $(A)$: The human body is exposed to a large number of infectious agents daily,yet only a few result in disease. Reason $(R)$: The human body possesses an immune system. Which option is correct for Assertion $(A)$ and Reason $(R)$?

What type of barrier is the mucus membrane?

Which of the following is related to humoral immunity?

Where do immature lymphocytes differentiate into antigen-sensitive lymphocytes?