What does '$a$' represent in the given figure?

Which secretion is responsible for the characteristic pungent odor in cockroaches?

Identify the location and function of the following structures in a cockroach:
$(i)$ Gizzard
$(ii)$ Hepatic caecum

The heart of a cockroach is........

Refer to the given figure of the female reproductive system of a cockroach and identify the correct labels (marked as $1, 2, 3$ and $4$) which are collectively called the genital pouch.

Each ovary in a cockroach is formed by a group of $8$ ovarian tubules or ovarioles,containing a chain of developing ova. Fill in the blank.