In cockroaches,$O_2$ is transported to the tissues by which of the following?

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

Complete the following statement :
$(a)$ In cockroach,grinding of food particles is performed by ........ .
$(b)$ Malpighian tubules help in the removal of ........ .
$(c)$ The hindgut of the cockroach is differentiated into ........ .
$(d)$ In the cockroach,blood vessels open into spaces called ........ .

If the head of a cockroach is removed,it may live for a few days because:

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.

In the male cockroach,in which part of the reproductive system are the sperms stored?