What is the function of the clitellum in an earthworm?

$A$ 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?

In earthworms,where is hemoglobin found?

What is the function of the typhlosole in an earthworm?

In which of the following are the nephridial funnels (nephrostomes) present?

In $Pheretima$,fertilization occurs in $.........$.