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

Why is the circulatory system of an earthworm called a closed type of circulatory system?

Select the correct option regarding blood plasma/fluid for humans and earthworms.

Enteronephric nephridia of Earthworm are:

Match the regions of the earthworm based on the clitellum:
$P$ - Segments $14$ to $16$
$Q$ - Segment $17$ to the last segment
$R$ - Segments $1$ to $13$
Identify the correct sequence for the Pre-clitellar region,Post-clitellar region,and Clitellar region,respectively.

Distinguish between the following: Prostomium and peristomium.