How many Malpighian tubules are present at the junction of midgut and hindgut in a cockroach?

The given figure shows the open circulatory system of a cockroach. Identify the structure that facilitates the flow of haemolymph by its contraction and relaxation.

Which one of the following has an open circulatory system?

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

Match the following columns regarding the anatomy of a cockroach:

Column-$I$	Column-$II$
$P$. Seventh sternum	$I$. Boat-shaped
$Q$. Eighth and ninth sterna	$II$. Anal cerci
$R$. Ninth sternum (in males)	$III$. Genital pouch
$S$. Tenth segment	$IV$. Anal styles

The figure given below shows the alimentary canal of a cockroach with a few structures labelled as $1, 2, 3$ and $4$. Identify the structure which is also called proventriculus and helps in grinding the food particles.