The enzyme carbamoyl phosphate synthetase requires:
Mg++
Ca++
K+
None of the above
One molecule of ammonia condenses with CO2 in the presence of two molecules of ATP to form carbamoyl phosphate. The reaction is catalyzed by the mitochondrial enzyme carbamoyl phosphate synthetase-I (CPS-I).
Reference: Vasudevan 7th  ed, pg 203