The locomotory organ of an earthworm is ..........

In earthworms,the clitellum is located in which segments?

Earthworm shows locomotion by means of

Identify $X$ and $Y$ from the given figure of the reproductive system of an earthworm:

Which of the following is responsible for destroying bacteria on the body surface of an earthworm?

Study the following in $Pheretima$.
$I.$ Dorso-intestinal blood vessels
$II.$ External intestinal plexus
$III.$ Internal intestinal plexus
$IV.$ Ventro-intestinal blood vessel
Arrange the blood vessels in the correct sequence of blood flow from the ventral blood vessel to the dorsal blood vessel.
The correct sequence is: