What is the function of nephridia?

Nephridia of Earthworm are analogous to

How is locomotion achieved in earthworms?

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

Identify the incorrect statements among the following:
$(a)$ In earthworm,a single male genital pore is present.
$(b)$ Setae help in locomotion of earthworm.
$(c)$ The muscular layer in the body wall of earthworm is made up of only circular muscles.
$(d)$ Typhlosole is a part of the intestine of earthworm.

What is the scientific name of the South Indian earthworm?