The excretory structure of $Amphioxus$ $(Cephalochordate)$ is:

Match the following:

Animal	Excretory organ/Unit
$(a)$ Balanoglossus	$(i)$ Metanephridia
$(b)$ Leech	$(ii)$ Nephridia
$(c)$ Locust	$(iii)$ Flame cells
$(d)$ Liver fluke	$(iv)$ Absent
$(e)$ Sea urchin	$(v)$ Malpighian tubule
$(f)$ Pila	$(vi)$ Proboscis gland

In vertebrates,what is the significance of the renal portal system?

In which one of the following organisms are its excretory organs correctly stated?

Match the excretory organs listed under column $I$ with the animals given under column $II$. Choose the answer which gives the correct combination of alphabets of the two columns.

Column $I$ (Excretory organs)	Column $II$ (Animals)
$A$. Nephridia	$p$. Hydra
$B$. Malpighian tubules	$q$. Leech
$C$. Protonephridia	$r$. Shark
$D$. Kidneys	$s$. Round worms,$t$. Cockroach

Discuss the evolution of excretory organs in various animal groups and mention their functions.