Which of the following is the least toxic nitrogenous waste?

$A$ bird excretes nitrogenous waste materials in the form of

Nitrogenous wastes are primarily excreted in the form of ........

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.

Separation of an amino group from an amino acid is known as:

In the ornithine cycle,which of the following wastes are removed from the blood?