Which of the following enzymes helps in the production of urea?

In the tissue cells,ammonia is produced by:

Ammonia is the main nitrogenous waste product in ........ .

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.

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

Frog is