Arthrodial membrane is present in..
Earthworm
Cockroach
Frog
Man
Identify $X$ the from the figure.
The given figure shows the digestive system of cockroach with few structures marked as $A , B , C$ and $D$.
Identify structures $A$ to $D$.
Give scientific reasons : In cockroach well developed respiratory system is seen.
The blood of cockroach contains no respiratory pigment. It means that