Blood glands of Pheretima occur in segments

Earthworms increase the . . . . . . of the soil.

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

$A$ transverse section of $Pheretima$ taken through the $10^{th}$ segment is observed under a microscope. Which of the following structures can be observed in the section?

Earthworms are known for having which of the following?

In $Pheretima$,the gizzard is responsible for..........