A female neonate did well until approximately 24 hours of age when she became lethargic. A sepsis workup proved negative. At 56 hours, she started showing focal seizure activity. The plasma ammonia...

A female neonate did well until approximately 24 hours of age when she became lethargic. A sepsis workup proved negative. At 56 hours, she started showing focal seizure activity. The plasma ammonia level was found to be 1,100 μmol/L (normal 5–35 μmol/L). Quantitative plasma amino acid levels revealed a marked elevation of argininosuccinate.
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Which one of the following enzymic activities is most likely to be deficient in this patient? EXPLAIN your answer
A. Arginase.
B. Argininosuccinate lyase.
C. Argininosuccinate synthase.
D. Carbamoyl phosphate synthetase I.
E. Ornithine transcarbamoylase.