Urea in human urine is derived from the breakdown of:

The most abundant metabolic waste product that is harmful and universal is ........ .

Match the following columns:

Column-$I$	Column-$II$
$P$. Ammonotelic	$I$. Bony fishes
$Q$. Ureotelic	$II$. Aquatic amphibians and insects
$R$. Uricotelic	$III$. Land snails and insects
	$IV$. Marine fishes
	$V$. Mammals
	$VI$. Terrestrial amphibians
	$VII$. Reptiles and birds

The characteristic that is shared by urea,uric acid and ammonia is/are:
$(A)$ They are nitrogenous wastes.
$(B)$ They all need very large amount of water for excretion.
$(C)$ They all are equally toxic.
$(D)$ They are produced in the kidneys.

Which of the following animals does not excrete nitrogen as urea?

Order of toxicity among ammonia,urea and uric acid (from lower to higher) is