The conversion of dangerous nitrogenous waste into less toxic excretory matter is carried out in man in the

How have terrestrial organisms adapted themselves for the conservation of water?

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.

Urea is physiologically produced by the action of the enzyme ........

In public urinals,the urine on standing gives a pungent smell,due to

For hypertonicity,urea is retained in