In $Pheretima$, the number of ring vessels per segment in $12^{\text{th}}$ and $13^{\text{th}}$ segments is: (in $pairs$)

In $Pheretima$,nephridia occur in:

One direct use of earthworms to farmers is:

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.

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.

Regarding blood circulation,it may be said that in $Pheretima$,the dorsal vessel is a: