In earthworms,where is hemoglobin found?

Earthworms are:

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:

In which region is the tuft of nephridia found in earthworms?

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

Chromophil cells in earthworms are found in the........