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.

Which of the following statement$(s)$ is/are correct about the nervous system of a cockroach?
$(i)$ It consists of a series of fused segmentally arranged ganglia joined by paired longitudinal connectives on the ventral side.
$(ii)$ There are six ganglia lie in the thorax,and three in the abdomen.
$(iii)$ The sense organs are antennae,eyes,maxillary palps,labial palps,and anal cerci,etc.
$(iv)$ Each eye consists of about $5000$ hexagonal ommatidia.

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 styles
$R$. $10$th segment	$III$. Genital pouch

In cockroaches,the excretory product is ........ .

Explain the digestive system of cockroach with the help of a labelled sketch.

The nerve cord in a cockroach is: ........