About how many times does the nymph of the Periplaneta americana undergo moulting before becoming an adult?

The given figure shows the digestive system of a cockroach with a few structures marked as $A, B, C$ and $D$. Identify structures $A$ to $D$.

Which one of the following is one of the paths followed by air or $O_2$ during respiration in the adult male $Periplaneta$ $americana$ as it enters the animal body?

Explain the nervous system of a cockroach.

How many ovarioles are found in each ovary of a cockroach?

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.