Which segments of the earthworm contain the clitellum?

Which are the sensory organs of an earthworm? Describe their functions.

Answer in one word or one line.
How many spermathecae are found in earthworm?

The clitellum of $Pheretima$ $posthuma$ is primarily associated with which of the following?

How many segments do earthworms have?

In $Pheretima$,there are red-coloured round bodies in the $4th$,$5th$,and $6th$ segments above the alimentary canal. They are believed to be involved in: