Which of the following is the correct representation of an antibody molecule?

How many types of memory cells are there in the immune system?

Passive acquired immunity can be obtained through the introduction of which of the following?

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?

What is produced by sensitized helper $T$-cells?